[Answerkey] UPSC Prelim-2018: Science MCQs solved with Explanation & Guessmaster-giri applicable in 4 out of 13 MCQs

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  1. Observations about the Science Qs in Pre18
  2. Strategy for Prelims-2019: Science Technology
  3. Answerkey for Prelims-2018 Science MCQs

Observations about the Science Qs in Pre18

  • In UPSC Prelims-2018 Paper-1, Total 13 out of 100 MCQs in GS Paper-1 were from Science portion. (Last Year only 6 Qs from Science)

UPSC Prelims 2018 Science MCQs Analysis

Science was mostly Contemporary & not Current

  • Only 3 MCQs from theory: Earth’s magnetism, Desert Leaf Modification and Plant disease spreaders.
  • Current Topic = upto one calendar year old (i.e. 1/1/2017 or newer) Only one MCQ can be pinpointed to last year’s current affairs with specific month and year i.e. Wannacry in May/June2017. Rest of the “non-theory” topics were in news since 2016.
  • Contemporary Topic = older than one calendar block. (i.e. before 1/1/2017).
  • So, out of 13 MCQs: 3 are from theory, 1 from Current and 9 from contemporary affairs.

Public Health se breakup, but ICT-Prem intensified

  • In earlier years, the examiner would ask minimum two to three MCQs from public health and within that, VIRUS used to be a favorite topic- be it Zika, Ebola, H1N1 or even theory of virus. But this year, no question from public health or Virus.
  • However, Examiner’s ICT-prem has intensified: In previous years he had asked about NFC, Project Loon, Lifi, OLED, Cert-IN. This year too, five MCQs from this segment (GPS Application, 3D printer Applications, iOT, Wannacry and Aadhar’s Open API).

Basic Physics prem continues

  • Last year asked about eLISA-Gravitational waves and Singularity-string theory. 2018: asked about why General theory of relativity has been in news?
  • However, arts-commerce graduates need not lose sleep over it because each year, at maximum, just 1-2 MCQs come from this area. But having said that….

Should not ignore Science for Prelims-2019

  • When UPSC asks tough Art & Culture MCQ, candidates became even more obsessed in preparing that subject Because Art & Culture again comes in GS-Mains Paper1.
  • Whereas, when tough Science questions are asked, candidates get more cynical and tend to ignore the subject altogether for Prelims. Because in GSMains Paper3, nowadays UPSC asking mostly generic / overall developments rather than asking about specific inventions, so why bother following individual science theory and individual invention?
  • But, looking at both 2017 and 2018 prelims, it’ll be a bad strategy to ignore Science for Prelims2019. Because other portions (Environment, Polity, Economy, History-Culture) are not getting any easier.
  • Even for CDS, CAPF, State services, science questions are not getting any easier. Both in CDS and CAPF there is a distinct pattern visible wherein science the examiner will ask from 11-12 NCERT or higher level. So, You’ve to stepup your game.

Strategy for Prelims-2019: Science Technology

  • Some Arm-Chair Generals looked at the Prelims-2018 paper superficially and are passing hasty & cynical judgements that “ye sab RANDOM-GK Hai, So for Prelims-2019, you should read LucentGK and StatePCS GK type books.” Well, it’s not true atleast for science.
  • After a stressful exam, it’s natural that candidates will also pass similar cynical remarks in online forums.
  • Yes, majority of the science MCQs are medium to tough level difficulty, but 11 out of 13 Science MCQs can be solved from routine books and newspapers only. They were not RANDOMGK / StatePCS type. So, at the end of all that ranting, you’ve to analyse the paper in a dispassionate manner, and accordingly finetune your preparation strategy for the 2019, if you can’t get selected in this round.

Science theory: How to prepare?

How to prepare Science for UPSC IAS Exam

  • Way back in 2013-14, UPSC asked very silly and easy questions from science like name of disease in absence of _ Vitamin. So, NCERT (Class7-10) + LucentGK type combo would have sufficed.
  • But in recent exams, hardly any direct questions are coming from there, as if UPSC examiner has stopped pampering the science-handicapped aspirants as well as those who’ve fully mastered it. For example, Newton’s principals and various laws of electricity, friction and optics, various uses of basic chemicals ….– nothing is asked in recent years. For the same reason, going through bulky General Studies Manuals, will give little benefit.
  • So, instead of finishing NCERT textbooks from first to last page, you should do selective study of chapters / topics having relevance with environment, agriculture, public health, biotech, space and ICT/communication. Give more weight towards Class 11-12.
  • Alternatively, you can go for NIOS Physics, Chemistry, Biology and Science Tech PDFs.
  • In Prelim-2018, 2 out of 13 science MCQs could be solved from NCERT / NIOS. True that ‘quantity wise’, it’s not a big number, they help you eliminate options, even in other current / contemporary science questions.

Science-tech Current Affairs: How to prepare?

Current Affairs means one calendar year before the exam (i.e. For Prelims-2019, it’ll be from 1/1/2018 onwards..) For this, you should prepare following:

  • In Prelim-2018, 2 out of 13 science MCQs could be solved from IYB, and it has also proved utility in other segments of the papers. So, (When it’s published next year): India Yearbook 2019 by Ministry of Information and Broadcasting. Focus on following chapters:
    • Ch.8 (Communication & IT),
    • Ch.16 (Health), Ch.25 (S & T Developments) and
    • Ch.31 (Diary of National Event).
    • Although past experience suggests that Ch.25 (Science) can be ignored because no science questions coming from there.
  • Daily reading of Indianexpress.
  • It’s true that Hindu gives more coverage to even obscure scientific research in nuclear / space / fundamental physics and one or two MCQs come from that area, but cost : benefit is poor. Besides, nowadays everyone following PDF compilations for Hindu, no need to reinvent the wheel by making your own notes for it. Because, even if nothing is asked from such PDF compilation- atleast you’re not at disadvantage, because everyone is at par with you. [Compared to a scenario where you spent numerous hours in making science current affairs note from theHindu and hardly gained one MCQ.]
  • Target areas should be: environment, agriculture, public health, biotech, ICT/communication and space. Within space, first priority to ISRO then NASA, then other countries and lastly to the randomly discovered stars and planets.

Science-tech Contemporary Affairs: How to prepare?

  • UPSC is different than other exams because both in prelims and mains, they’ll ask about events that happened even more than 1 year ago.
  • Infact both in Mains2017 and Prelim-2018- majority of the non-theory science questions were from events that occurred more than one year ago from the date of exam. In other words, contemporary portions dominates more than current affairs- in Science tech.
  • For this segment, you can refer to Ravi Agrahari’s Science & Tech Book (Macgrawhill) | हिंदी में भी उपलब्ध. The book is useful for both prelims and Mains. In Prelims2017, five out of 13 questions could be solved from here.
  • Target areas should be same as current affairs. environment, agriculture… and so forth.

Answerkey for Prelims-2018 Science MCQs

Now let’s solve the science questions from Prelims-2018 GS Paper:

Physics / Gravity / Nuclear

Q2. Consider the following phenomena : (Pre18 Set-D)

  1. Light is affected by gravity.
  2. The Universe is constantly expanding.
  3. Matter warps its surrounding space-time.

Which of the above is/are the prediction/predictions of Albert Einstein’s General Theory of Relativity, often discussed in media ?

  1. 1 and 2 only
  2. 3 only
  3. 1 and 3 only
  4. 1, 2 and 3

Difficulty: Tough because not given in routine study material, Guessmaster-giri not applicable, and most candidates don’t prepare basic-physics related theory / current affairs in this much detail, because it has almost zero utility in the Mains.

  • 2010: International Team of Astronomers confirmed Albert Einstein’s theory of general relativity and that the expansion of the universe is accelerating after looking at data from the Hubble Space Telescope…. there is an unknown source of energy in the universe which is causing the cosmic expansion to speed up. [Ref: TheHindu1]; 2016: Japanese researchers’ study finds that the expansion of the universe could be explained by a cosmological constant, as proposed by Einstein in his theory of general relativity. [Ref: TheHindu] So second statement is right. This eliminates B and C.
  • In the remaining options A and D, both have “statement1” common, so we’ve to believe that statement1 is right- Light is indeed affected by gravity, no need to find any reference.
  • 2018: Hubble Space Telescope captured image of a phenomenon called Einstein Ring. Einstein in his theory of general relativity, had suggested that a massive object would warp space and time. So, statement3 is right. [Ref: Foxnews, BBC Page and Random Google Book #1 ]
  • Hence we are left with correct answer “D”: 1, 2 and 3 all correct.

Some people are doing Hairsplittery that question is not asking what is in that theory, but whether it’s often in news? So, accordingly, either the answer is “B: only 3” or entire MCQ is invalid. But I go with Option D.

Biology / Botany / Biotech

Q4. Consider the following pairs of Terms sometimes seen in news vs Context /Topic: (Pre18 Set-D)

  1. Belle II experiment: Artificial Intelligence
  2. Blockchain technology: Digital/ Cryptocurrency
  3. CRISPR — Cas9: Particle Physics

Which of the pairs given above is/are correctly matched ?

  1. 1 and 3 only
  2. 2 only
  3. 2 and 3 only
  4. 1, 2 and 3

Difficulty: Medium because everyone knows #2 is right (Blockchain = Cryptocurrency), but that alone doesn’t help arriving at right answer, until you’ve the factualGK about CRISPR. Although CRISPR got frequent mention in both IndianExpress and theHindu’s science articles throughout 2017, so can’t say classify it in Tough MCQ.
Answer: Ravi Agrahari’s Science & Tech Book (Macgrawhill) | हिंदी में भी उपलब्ध PartB: Recent news in Science (Kindle Kindle Locations 25651-25652)

  • CRISPR, a new genome editing tool, could transform the field of biology. It allows scientists to edit genomes with unprecedented precision. So, #3 is wrong, CRISPR is definitely not associated with Particle Physics. This eliminates A, C and D. Thus we are left with answer “B: only 2”
  • Now, Just to satiate my curiosity- what was Belle-II experiment? Ans. It was conducted in Tsukuba, Japan to study violations of the Standard Model of particle physics. So, #1 is wrong. [Ref: IndianExpress 2017-April] But even if you had known that, you’d be still stuck between B or C. So, entire question hangs on whether you know about CRISPR or not.

I could classify that as ICT (because Blockchain is asked) , but since right answer depends on CRISPR-the-GENOME-editing tool, so I’ve put it under Biology / Biotech.

Q42. Consider the following statements: (Pre18 Set-D)

  1. The Earth’s magnetic field has reversed every few hundred thousand years.
  2. When the Earth was created more than 4000 million years ago, there was 54% oxygen and no carbon dioxide.
  3. When living organisms originated, they modified the early atmosphere of the Earth.

Which of the statements given above is/are correct?

  1. 1 only
  2. 2 and 3 only
  3. 1 and 3 only
  4. 1, 2 and 3

Difficulty: Tough because it ‘tests’ your understanding of the concepts given in Class12 NCERT geography / biology, and in the real-exam stress, difficult to take a call on #3.
First statement is right

  • On the scale of a million years, the earth’s magnetic fields has been found to reverse its direction. (NCERT Physics Class12 ch5 Page 189). “Million” = 10 lakh. “Hundred thousands” = some figure in lakhs. So, If we don’t engage in Hairsplittery about these two figures, then first statement is right. This eliminates B.

Second Statement is WRONG

  • There are three stages in the evolution of the present atmosphere….The early atmosphere largely contained water vapour, nitrogen, carbon dioxide, methane, ammonia and very little of free oxygen. (NCERT Class11 Physical Geo, ch2, page17).
  • There was no atmosphere on early earth. Water vapour, methane, carbondioxide and ammonia released from molten mass covered the surface. (NCERT Biology Clas12 Ch7 page 127)
  • So, both textbooks prove that CO2 was present, So, #2 wrong = Option B and D are eliminated.

Third Statement is ALSO WRONG

  • “early atmosphere of earth was modified by solar winds. This happened not only in case of the earth, but also in all the terrestrial planets, which were supposed to have lost their primordial atmosphere through the impact of solar winds.” [NCERT Class11 Physical Geo, ch2, page17]
  • Early atmosphere of earth had no free oxygen, the (life) forms until then could at best be only “anaerobic”. Chlorophyll–bearing organisms later released free oxygen which gave greater possibilities for life to evolve. [NIOS Biology Page5].
  • The first non-cellular forms of life could have originated 3 billion years back….(then) About 2000 million years ago the first cellular forms of life appeared on earth. Some of these cells had the ability to release Oxygen. [NCERT Biology Class12 Ch7 on Evolution]
  • Combining information from above three sources, it means early atmosphere of the earth was (mainly) modified by solar winds. When living organisms originated, it was beyond their capacity to modify the early atmosphere, since they couldn’t synthesize oxygen at that time. Britannica also says: Hundreds of millions of years separated the first biological production of oxygen by unicellular organisms and its eventual accumulation in the atmosphere. [यानि की शुरूआती सजीवो की शुरूआती वातावरण बदलने की औकात ही नही थी क्योकि उन्हें ऑक्सीजन बनाना नही आता था.]
  • Ofcourse, biodegradation of dead anaerobic micro-organism could have affected the levels of Carbon Dioxide and Nitrogen but they had such miniscule biomass, so % gas composition wise, these biochemical reactions would have made little impact on early atmosphere. They wouldnot have MODIFIED the atmosphere, unlike the other factors such as solar winds, degassing of the planet, geological carbon cycle etc.
  • This eliminates Statement#3, Thus we are left with answer “A: Only 1”.
  • I classify this as MCQ under biology section, because the ultimate answer depends on how initial living organisms behaved.

This is an ANTI-Guessmaster question, because GM-Rule#2: statements with dates, numbers, figures are wrong. so, Statement#2 has to be wrong, this eliminates B and D. But still real answer depends on whether #3 is right or not. But then, Guessmasters would guess casually that planktons and plants released oxygen so early atmosphere changed, but going by the textbooks- it’s not true.

Q84. Consider the following: (1) Birds (2) Dust blowing (3) Rain (4) Wind blowing. Which of the above spread plant diseases? (Pre18 Set-D)

  1. 1 and 3 only
  2. 3 and 4 only
  3. 1, 2 and 4 only
  4. 1, 2, 3 and 4

Difficulty: Tough because in real-exam stress, you’ve to make a call on whether rain can also spread plant disease or not?

  • Birds (#1) moving through crops can carry pathogens from the infected plant to other plans. Woodpeckers carry spores of tree pathogens. [Ref- Google Book1]
  • Some plant pathogenic bacteria are carried to short distance by wind (#4). In some places, rain seems to be more important than insects in disseminating the fire blight bacteria, by its washing or splattering effect of rain. (#3). [Ref-Google Book2 ]
  • There is only Option D where 1, 3 and 4 are together. So, “D” has to be the correct option.

Guessmaster-giriTM is Possible: GM-rule#4 that in UPSC “3tf MCQ” (3-statement-true/false), IF each individual statement contains barely 1-2 words then all of them are correct. Ofcourse, this MCQ has four statements but the skeleton is similar, so, you directly get the right answer D: 1, 2, 3, and 4; #WITHOUT-STUDYING-ANYTHING.

Q3. With reference to the Genetically Modified mustard (GM mustard) developed in India, consider the following statements : (Pre18 Set-D)

  1. GM mustard has the genes of a soil bacterium that give the plant the property of pest-resistance to a wide variety of pests.
  2. GM mustard has the genes that allow the plant cross-pollination and hybridization.
  3. GM mustard has been developed jointly by the IARI and Punjab Agricultural University.

Which of the statements given above is/are correct ?

  1. 1 and 3 only
  2. 2 only
  3. 2 and 3 only
  4. 1, 2 and 3

Difficulty: Medium because you’ve to know specific factual GK that it was developed by Delhi University’s centre. But since it frequently came in GM-related topics in newspapers and magazines during 2016 and 2017, hence not classifying it as ‘tough’.

  • GM Mustard is a perfect flower so it ‘self-pollinates’. Therefore Delhi University’s then VC Dr. Deepak Pental created GM mustard so that he could cross-pollinate Indian variety with European variety to make new hybrid called DMH-11. Hence #2 is right and #3 is wrong. Ref: My lecture on Youtube It was a hot topic for Mains-2016, then again resurfaced in 2017-October when GEAC stalled the permission.
  • Anyways, since it was developed in DU centre, the third statement is wrong and by elimination, we are left with answer B: Only 2.

Guessmaster-giriTM is Possible: GM-rule#3 that in UPSC MCQs, Parent organization-walle statements are always wrong, then #3 ought to be wrong and by elimination, we’ve the correct answer B ; #WITHOUT-STUDYING-ANYTHING. (and Statement#1 should also be wrong because it has extreme word “Wide Variety”)

Q17. Which of the following leaf modifications occur(s) in the desert areas to inhibit water loss? (Pre18 Set-D)

  1. Hard and waxy leaves
  2. Tiny leaves
  3. Thorns instead of leaves

Select the correct answer using the code given below :

  1. 2 and 3 only
  2. 2 only
  3. 3 only
  4. 1, 2 and 3

Difficulty: Tough because it’s vaguely worded about “leaf modification” and Thorn vs Spine.


  • Thorn is not a ‘leaf modification’, it is an ‘aerial modification of stem’. (Ref: NIOS Biology page159);
  • Spine” is a leaf modification to protect the plant and help in reducing transpiration. (Ref: NIOS Biology page176);
  • Some desert plants like Opuntia , have no leaves – they are reduced to spines–and the photosynthetic function is taken over by the flattened stems. (Ref: NCERT Biology class12 ch.13 page225)
  • So, third statement is wrong- thorn is not a leaf modification, spine is a leaf modification. This eliminates A, C and D. Thus we are left with correct answer B: only2. (but that doesn’t feel right- entire question seems wrongly worded / framed.)

Counter argument: Answer is “D”: 1, 2 and 3.

  • Because, Same question was asked in UPSC Prelims 2013 (Set A Q.94). And in the official Answerkey, released by UPSC, the answer was “D”: 1, 2 and 3. Therefore, answer has to be “D”.
  • Additionally, Even Goh Cheng Leong Page 136 mentioned that “Desert plants have few or no leaves, and the foliage is either waxy, leathery, hairy or needle shaped to reduce water loss through transpiration. Some of them are entirely leafless, with pricks or thrones.

Guessmaster-giriTM is Possible: GM-rule#4 that in UPSC “3tf MCQ” (3-statement-true/false), IF each individual statement contains barely 1-2 words then all of them are correct. Ofcourse, this MCQ has statements with more 2 words but still the skeleton is similar, so, you directly get the right answer D: 1, 2 and 3; #WITHOUT-STUDYING-ANYTHING.

Since UPSC has lifted this from old question bank, so they’d have also copied answer from the same question bank, therefore in all likelihood, default answer will be D, until someone raises objection and UPSC admits the mistake of using wrong words thrones/spines- which is very unlikely given their arrogance, although they did admit mistake of setting wrongly worded MCQ once upon a time in EPFO exam.

ICT / Computer / Mobile

Q6. When the alarm of your smartphone rings in the morning, you wake up and tap it to stop the alarm which causes your geyser to be switched on automatically. The smart min-or in your bathroom shows the day’s weather and also indicates the level of water in your overhead tank. After you take some groceries from your refrigerator for making breakfast, it recognises the shortage of stock in it and places an order for the supply of fresh grocery items. When you step out of your house and lock the door, all lights, fans, geysers and AC machines get switched off automatically. On your way to office, your car warns you about traffic congestion ahead and suggests an alternative route, and if you are late for a meeting, it sends a- message to your office accordingly. In the context of emerging communication technologies, which one of the following term” best applies to the above scenario? (Pre18 Set-D)

  1. Border Gateway Protocol
  2. Internet of Things
  3. Internet Protocol
  4. Virtual Private Network

Difficulty: Easy if you’re following the tech-news regularly. Or, if you have common understanding of ICT to know that passage is definitely not talking about BGP, IP, VPN.
Answer: Ravi Agrahari’s Science & Tech Book (Macgrawhill) | हिंदी में भी उपलब्ध ch. 14 Internet (Kindle Locations 9750-9752)
The IoT is the network of physical objects which are accessed through the Internet. Internet of Things (IoT) has a broad scope, a heart patient can do heart monitoring easily, farm animals can be easily sensed with a help of biochip transponder, an automobile that has built-in sensors can alert the driver when tire pressure is low.
Q40. In which of the following areas can GPS technology be used? (Pre18 Set-D)

  1. Mobile phone operations
  2. Banking operations
  3. Controlling the power grids

Select the correct answer using the code given below:

  1. 1 only
  2. 2 and 3 only
  3. 1 and 3 only
  4. 1, 2 and 3

Difficulty: Easy, by common understanding of what is GPS and creative thinking about how and where it could be used.

  • 2018: Government’s EASE framework for Public sector Banks provides for developing mobile app to locate nearest ATMs (so that can be possible only via GPS.) [REF: PIB]. In 2016, PNB bank had already launched android mobile apps enabling the customer to locate nearest PNB ATM using GPS. [Ref: TheHindu] so, yes second statement is right, GPS can indeed be used in Banking operations. This eliminates “A” and “C”, because they don’t contain statement#2.
  • In the remaining options B and D- have “statement#3” in common, so we must accept that GPS can indeed be used in controlling powergrids. No need to waste time finding proof.
  • 2016: The Department of Telecom has mandated that mobile phones sold in India will come with a dedicated ‘panic button’ and Global Positioning System (GPS) facility that can be used to send out a signal in case of distress. This is aimed at improving the safety of women and ensuring a quick response from security agencies. [Ref: IYB ch.8 on communication] So, first statement is right. This we are left with correct answer, D: 1, 2 and 3.
  • Some people are engaged in Hairsplittery that “mobile operation itself doesn’t need GPS, but cell tower and spectrum. Hence answer should be”B: (2 and 3 only)“.” But I still go with D.
  • Sidenote: While GPS as such as “Space technology”, but here it’s asked in context of “smart applications”, so putting it under ICT.

Guessmaster-giriTM is Possible, if you go by GM-rule#4 that in UPSC “3tf MCQ” (3-statement-true/false), IF each individual statement contains barely 1-2 words then all of them are correct. Thus, you directly get the right answer D: 1, 2 and 3; #WITHOUT-STUDYING-ANYTHING.

Q43. The terms ‘Wanna Cry, Petya and Eternal Blue’ sometimes mentioned in the news recently are related to (Pre18 Set-D)

  1. Exo-planets
  2. Crypto-currency
  3. Cyber attacks
  4. Mini satellites

Difficulty: Easy, if you’re following any newspaper – because Wannacry / Petya ransomware was in news during 2017-May / June.

  • Wannacry ransomware locks user’s devices and prevents them from accessing data and software until a certain ransom is paid to its creator. [Ref: IndianExpress ]
  • Like WannaCry, “Petya” worm spreads rapidly through networks that use Microsoft Windows, and demands $300 paid in bitcoin to unlock your infected PC. [Ref: IndianExpress ]
  • EternalBlue is the name given to a software vulnerability in Microsoft’s Windows operating system, because of which aforementioned ransomwares spread.
  • So, all these terms are related to cybersecurity.

Q54. “3D printing” has applications in which of the following? (Pre18 Set-D)

  1. Preparation of confectionery items
  2. Manufacture of bionic ears
  3. Automotive industry
  4. Reconstructive surgeries
  5. Data processing technologies

Select the correct answer using the code given below :

  1. 1, 3 and 4 only
  2. 2, 3 and 5 only
  3. 1 and 4 only
  4. 1, 2, 3, 4 and 5

Difficulty: Easy through elimination and basic idea of the 3d printing technology.
Answer: Ravi Agrahari’s Science & Tech Book (Macgrawhill) | हिंदी में भी उपलब्ध (Kindle Location 25643).

  • Bioprinting process in which living tissues can be 3d-printed using stem-cell containing bioink. This means 3D printing has applications in bionic ears (#2) and reconstructive surgeries (#4). There is only one option where 2 and 4 are together i.e. Option D: all statements correct.
  • Ofcourse, some people have doubt, how can 3D printing find utility in data processing (#5). So let’s crosscheck: U.S. Air Force Research Laboratory (AFRL) has developed 3D printed circuitry to produce a flexible Silicon-on-polymer chip. This new chip has a memory more than 7,000 times larger than any comparable commercially available devices. [Webreport: 2018 January], Therefore #5 is also right.

Guessmaster-giriTM is Possible, if you go by GM-rule#4 that in UPSC “3tf MCQ” (3-statement-true/false), IF each individual statement contains barely 1-2 words then all of them are correct. Ofcourse, this MCQ has five statements but the skeleton is similar, so, you directly get the right answer D: 1, 2, 3, 4 and 5; #WITHOUT-STUDYING-ANYTHING.

Q62. The identity platform ‘Aadhaar’ provides open “Application Programming Interfaces (APIs)”. What does it imply? (Pre18 Set-D)

  1. It can be integrated into any electronic device.
  2. Online authentication using iris is possible.

Which of the statements given above is/are correct ?

  1. 1 only
  2. 2 only
  3. Both 1 and 2
  4. Neither 1 nor 2

Difficulty: Medium. You’ve to know the meaning of Open API. I don’t classify it as ‘tough’, because the meaning is given in India Yearbook 2018.
Answer: Open Application Programming Interfaces (APIs): This is government’s approach to promote software interoperability for all e-governance applications and systems and provide access to data and services for promoting participation of all stakeholders including citizens. [Ref: IYB Ch. 8 on Communication] From above description, it appears that open API is a concept like ‘open source technology’, anyone can use the code to develop apps / portals / software. We can further refine our understanding using Electronics Ministry’s Policy on Open API. An Open API has following characteristics:

  • Open APIs shall be provided free of charge to other Government organizations and public (whenever possible).
  • They shall be properly documented with sample code and sufficient information for developer s to make use of the Open API.
  • Open APIs adhere to national cyber security policy.
  • They’re stable and scalable. They’re platform independent, language independent.

Now coming back to Aadhar’s “Open API”:

  • Does such “Open API” allow Aadhar’s integration in any electronic device (like digital alarm, music player or pendrive?) So, statement#1 is wrong, because it’s extreme hyperbole.
  • Similarly, while an independent developer could design an app / software / technology to implement #2 but, it’s irrelevant to the ‘open’ concept of API. That’s just as irrelevant as saying “Accessing banned torrent sites is possible via Tor Browser because it is built using Mozilla Firefox’s Open source technology.”
  • So, both statements are wrong (Option D).

Counter-argument: These features are lifted Verbatim from Nandan Nilekani’s Blog in TimesofIndia in 2016, where he said, ” Aadhaar provides open Application Programming Interfaces or APIs, which can be integrated easily into any electronic device. These APIs enable online authentication using a fingerprint or iris.” Therefore both statements are right (Option C).

GM-Rule#1: All extreme worded statements are wrong. so, first statement has term “any device” so it must be wrong, But since it’s a disputed MCQ- either both are right or both are wrong. So, whether Guessmaster-giri was helpful in this Question? Can’t say until official answerkey is released by UPSC.

Space Tech / ISRO Related

Q1. With reference to the Indian Regional Navigation Satellite System (IRNSS), consider the following statements : (Pre18 Set-D)

  1. IRNSS has three satellites in geostationary and four satellites in geosynchronous orbits.
  2. IRNSS covers entire India and about 5500 sq. km beyond its borders.
  3. India will have its own satellite navigation system with full global coverage by the middle of 2019.

Which of the statements given above is/are correct?

  1. 1 only
  2. 1 and 2 only
  3. 2 and 3 only
  4. None

Difficulty: As such every serious aspirant knows about IRNSS is our DESHI-GPS, but in real exam, quite possible that you’ll get confused over how many stationary vs synchronous satellites does it have? Topic was in news from 2013 to 2016. Afterwards, last two years’ India Yearbooks – 2017 and 2018, are mentioning this topic but not covering the specific factoids asked here. Considering all facets, I classify it as medium to tough MCQ (Multi Choice Question).
Answer: Ravi Agrahari’s Science & Tech Book (Macgrawhill) | हिंदी में भी उपलब्ध Ch.10 (Kindle Locations 6736-6737)

  • In IRNSS, Out of the seven satellites of space segment; four satellites are in geosynchronous orbit and three satellites are in geostationary orbit. So 1st statement is right. “D” is eliminated. [And we no longer need to worry about the validity of statement #3, because there is no option where 1 and 3 are together.]
  • IRNSS covers an area of about 1,500 km around India. So, 2nd statement is wrong. B and C are eliminated. Therefore, Answer has to be A) 1 only.
  • Agni V is an intercontinental ballistic missile (ICBM) with a range of 5,500 to 5,800 km. So, can IRNSS cover “inter-continental” range of 5500 sqkm area beyond border? इतनी जोरदार DESHI-GPS बनाने की अपनी औकात है ही नही…It’s a hyperbole “extreme” statement. on that logic also, second statement ought to be wrong.

ANTI-Guessmaster question. If you go by GM-rule#2 that in UPSC MCQs, all statements with dates, numbers, figures are usually wrong, then here all three statements contain figures- Even first statement has figures (4) and (3) so answer should be “D:NONE”- but that’s a wrong answer.

Q80. With reference to India’s satellite launch  vehicles, consider the following statements: (Pre18 Set-D)

  1. PSLVs launch the satellites useful for Earth resources monitoring whereas GSLVs are designed mainly to launch communication satellites.
  2. Satellites launched by PSLV appear to remain permanently fixed in the same position in the sky, as viewed from a particular location on Earth.
  3. GSLV Mk III is a four-staged launch l vehicle with the first and third stages l using solid rocket motors; and the second and fourth stages using liquid rocket engines.

Which of the statements given above is/are correct.?

  1. 1 only
  2. 2 and 3
  3. 1 and 2
  4. 3 only

Difficulty: Medium because for you need to recall so many factoids / concepts just to answer a single MCQ.
Answer: Ravi Agrahari’s Science & Tech Book (Macgrawhill) | हिंदी में भी उपलब्ध (Kindle Locations 6062-6063).

  • ISRO developed PSLV to launch satellites into polar orbits and GSLV to launch geosynchronous satellites into geostationary orbits. Geostationary satellites orbit around the earth in 24 hours and since the earth rotates with the same period, the satellite would appear fixed from any point on earth. So, statement#2 is wrong. This eliminates option B and C.
  • GSLV is a 3-stage launch vehicle, where first 2 stages are similar to PSLV with same solid and liquid nature of fuel but the third stage is completely different, i.e., cryogenic stage. So third statement is WRONG. This eliminates B and D.
  • Thus we’re left with answer A: only 1.

Guessmaster-giriTM is possible, to an extend

  • GM-Rule#2: statements with dates, numbers, figures are wrong. Look at third statement, it talks about four (4) stage, first and third stage…. so, these are all figures / numbers written in words. So, #3 has to be wrong.
  • GM-Rule#5: Word association. Second statement is talking about “Geostationary satellites.” and full form of GSLV is “Geostationary Satellite Launch Vehicle (GSLV)”, that means by ‘word-association’, the PSLV is not ‘fitting in’, so #2 has to be wrong. By elimination we are left with correct answer A: 1 Only. However, here you needed to know the full forms and concepts before applying the GM-rule, so can’t say that you could get the right answer #WITHOUT-STUDYING-ANYTHING.

Stay tuned for the remaining parts of the Answerkey. You can get free email updates whenever I post new article, by filling up this form.


I neither encourage nor condone shortcuts / hacks / cheatcodes for success in exams. The purpose of using the term Guessmaster-giriTM with Hashtag #WITHOUT-STUDYING-ANYTHING = It’s my wishful thinking that UPSC examiner will take a note of this nuisance going on in recent years, and will stop such opportunities in the future exams, and if that doesn’t happen- atleast everyone should benefit from this knowledge.

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96 Comments on “[Answerkey] UPSC Prelim-2018: Science MCQs solved with Explanation & Guessmaster-giri applicable in 4 out of 13 MCQs”

  1. Ur analysis is great mrunal…..
    I m waiting for more questions….
    काश कि आप सभी विषय पढ़ाते जैसा आप economy पढ़ाते हैं।
    You are awesome in the field of civil services…

  2. Sir,
    I have a doubt regarding the Aadhar Open API Question.
    I have worked as a Software Developer for 2 years and as part of my job, I used to write APIs.
    APIs are used to exchange data/services(b/w server and client machine), so Statement2 seems to be correct because as part of Open Aadhar API, the Aadhar’s server could provide for authentication of Iris scans.
    But Statement-1 is tricky, APIs generally use HTTP protocol(i.e as of now, IOT devices uses some other protocol such as MQTT, etc), and for that internet connectivity(or GPRS connectivity) is required. The statement had ‘any’ electronic device which makes the statement incorrect.
    Can you please confirm. Every coaching centre’s answer key has given option C/D.

    1. Our watch,washing machine(with digital display),inverter etc. are also considered as electronic device….If there was “an” instead of “any” then the first statement would be correct.

    2. As extreme it may sound, but in theory and in practice, it is fully possible to embed a fingerprint/iris scanner into a “pendrive”, “music player” or any other physical/electronic object.
      And in the interest of separation of concerns, the Aadhaar API at the server would care least about which electronic device the request originated from as long as it follows the agreed protocol, encryption, etc.

  3. sir upload remaining subject ASAP,varna bhul jayenge paper kya diya tha

  4. The question about whether the early atmosphere of the earth was modified by living organisms or not is explained in ‘Gaia hypothesis’.

  5. Sir please provide your current daily affairs notes,and other subject notes of upsc

  6. Einstein’s general theory of relativity assumes a STATIC universe and therefore includes the cosmological constant.Expanding universe is NOT a prediction of general theory of relativity.

  7. sir, please continue your online classes over youtube.

  8. IRNSS https://www.isro.gov.in/irnss-programme
    The space segment consists of the IRNSS constellation of eight satellites, NavIC. Three satellites are located in suitable orbital slots in the geostationary orbit and the remaining four are located in geosynchronous orbits with the required inclination and equatorial crossings in two different planes. All the satellites of the constellation are configured identically. The satellites are configured with I-1K Bus to be compatible for launch on-board PSLV.

    what i wonder is what about the eighth satellite

  9. Sir, the second statement is given that –
    IRNSS covers entire India and about (5500 sq. km) beyond its borders.

    Generally range is given in kilometers. For irnss this range is 1500 km. But in this question area coverd by irnss is given in sq* KMs. But in this question instead of asking the range they are asking about area coverd.
    Sir, according to this logic is this statment right or wrong?

  10. The question with general theory of relativity:
    Just google Einstein’s static universe.
    Einstein predicted that universe is constant… And later accepted it as his error… So general theory of relativity never predicted expanding universe…

  11. Einstein theory never predicted expanding universe.

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