UPSC PRELIMS 2020- Sci & Tech Answer keys with Explanation

Dear Aspirants,

This post covers the answer keys and the references for them for the questions based on Science and Technology. As far as references are concerned, you will find links and pdfs by Government bodies, Newspapers and Research organisations. You are requested to go through them.

If you wish to represent your grievances regarding the question or its options to UPSC you can visit https://upsconline.nic.in/miscellaneous/QPRep/rlogin.php?year=2020&exam=CSP#hhh1

The last date is 11th October 2020.

My further posts will cover the questions based on other topics like Environment, History, Geography, Indian Polity etc...

With reference to carbon nanotubes, consider the following statements :

1.They can be used as carriers of drugs and antigens in the human body.

2.They can be made into artificial blood capillaries for an injured part of humanbody.

3.They can be used in biochemical sensors.

4.Carbon nanotubes are biodegradable.

Which of the statements given above are correct?

(a) 1 and 2 only

(b) 2, 3 and 4 only

(c) 1, 3 and 4 only

(d) 1, 2, 3, and 4

Reference :

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4114241

https://www.hindawi.com/journals/bmri/2013/578290

Consider the following activities :

1. Spraying pesticides on a crop field

2. Inspecting the craters of an active volcano

3. Collecting breath samples from spouting whales for DNA analysis

At the present level of technology, which of the above activities can be successfully carried out using drones?

(a) 1 and 2

(b) 2 and 3

(c) 1 and 3

(d)1, 2 and 3

Reference:

https://whale.org/can-drones-help-whales/

https://www.commercialdroneprofessional.com/case-study-monitoring-active-volcanoes-with-the-help-of-drones/

https://www.thehindu.com/news/national/telangana/crop-dusting-using-drones-is-illegal-says-centre/article30706526.ece

Remarks: Till date Government of India has not allowed spraying fertilizer on a crop field but as the question is in general context option 1 can be considered as correct.

The experiment will employ a trio of spacecraft flying in formation in the shape of equilateral triangle that has sides one million km long, with lasers shining between the craft.” the experiment in the question refers to?

(a) Voyager-2

(b) New horizons

(c) LISA pathfinder

(d) Evolved LISA

Reference: https://www.thehindu.com/sci-tech/science/Space-antennae-to-probe-gravitational-waves/article14433813.ece

Consider the following statements :

1. Genetic changes can be introduced in the cells that produce eggs or sperms of a prospective parent

2. A person’s genome can be edited before birth at the early embryonic stage

3. Human induced pluripotent stem cells can be injected into the embryo of a pig.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 and 3 only

(c) 2 only

(d) 1, 2 and 3

Reference:

https://medlineplus.gov/genetics/understanding/mutationsanddisorders/genemutation/

https://www.ncbi.nlm.nih.gov/books/NBK447276/#sec_179

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5025037/

https://www.geneticsandsociety.org/internal-content/what-human-gene-editing#:~:text=Genome%20editing%20is%20a%20way,change%20genes%20in%20living%20organisms.

What is the importance of using pneumococcal conjugate vaccines in India?

1. These vaccines are effective against pneumonia as well as meningitis and sepsis.

2. Dependence on antibiotics that are not effective against drug-resistant bacteria can be reduced.

3. These vaccines have no side effects and cause no allergic reactions

Select the correct answer using the given code below-

(a) 1 only

(b) 1 and 2 only

(c) 3 only

(d) 1, 2 and 3

Reference:

https://www.thestatesman.com/india/why-india-is-introducing-pneumococcal-conjugate-vaccine-or-pcv-1502643216.html

https://nhm.gov.in/New_Updates_2018/NHM_Components/Immunization/Guildelines_for_immunization/Operational_Guidelines_for_PCV_introduction.pdf

https://www.sciencedirect.com/science/article/pii/S1201971219303972

Which of the following statements are correct regarding the general difference between plant cells and animal cells?

1. Plant cells have cellulose cell walls whilst animal cells do not.

2. Plant cells do not have plasma membrane unlike animals cells which do

3. Mature plant cell has one large vacuole whilst animal cell has many small vacuoles

Select the correct answer using the given code below-

(a) 1 and 2 only

(b) 2 and 3 only

(c) 1 and 3 only

(d) 1, 2 and 3

Reference:

https://microbenotes.com/plant-cell-vs-animal-cell/

Which of the following are the reasons/factors for exposure to benzene pollution?

1. Automobile exhaust

2. Tobacco smoke

3. Wood burning

4. Using varnished wooden furniture

5. Using products made of polyurethane 

Select the correct answer using the given code below-

(a) 1, 2 and 3 only

(b) 2 and 4 only

(c) 1, 3 and 4 only

(d) 1, 2, 3, 4 and 5 only

Reference:

http://www.cpcbenvis.nic.in/cpcb_newsletter/BENZENE%20IN%20AIR%20AND%20IT'S%20EFFECT%20ON%20HUMAN%20HEALTH.pdf

https://education.seattlepi.com/environmental-impacts-polyurethane-foam-6242.html

In the context of the recent advances in human reproductive technology, Pro nuclear technology is used for:

(a) Fertilization of egg into vitro by the donor sperm

(b) Genetic modification of sperm producing cells

(c) Development of stem cells into functional embryos

(d) Prevention of mitochondrial diseases in offspring

Reference:

https://www.nature.com/articles/nature08958

With the present state of development Artificial Intelligence can effectively do which of the following?

1. Bring down electricity consumption in industrial units

2. Create meaningful short stories and songs

3. Disease diagnosis

4. Text to speech conversation

5. Wireless transmission of electrical energy

Select the correct answer using the given code below-

(a) 1, 2, 3 and 5 only

(b) 1, 3 and 4 only

(c) 2, 4 and 5 only

(d) 1, 2, 3, 4 and 5

With reference to the “Visible Light Communication” technology, Which of the following statements are correct?

1. VLC uses electromagnetic spectrum wavelengths 375 to 780 nm

2. VLC is known as long range optical wireless communication

3. VLC can transmit large amounts of data faster than bluetooth

4. VLC has no electromagnetic interference

Select the correct answer using the given code below-

(a) 1, 2 and 3 only

(b) 1, 2 and 4 only

(c) 1, 3 and 4 only

(d) 2, 3 and 4 only

Reference:

https://www.sciencedirect.com/science/article/pii/S2352864816300335

Visible Light Communication (VLC) systems employ visible light for communication that occupy the spectrum from 380nm to 750nm.

With reference to the Blockchain Technology, consider the following statements:

1. It is a public ledger that everyone can inspect, which no single user controls 

2. The structure and design of blockchain is such that all the data in it are about cryptocurrency only

3. Applications that depend on the basic features of blockchain can be developed without anybody’s permission

Which of the statements given above is/are correct?

(a) 1 only

(b) 1 and 2 only

(c) 2 only

(d) 1 and 3 only

Reference:

https://niti.gov.in/sites/default/files/2020-01/Blockchain_The_India_Strategy_Part_I.pdf

What are the advantages of fertigation in agriculture?

1.Controlling the alkalinity of irrigation water is possible.

2. Efficient application of Rock Phosphate and all other phosphatic fertilizers is possible.

3. Increased availability of nutrients to plants is possible.

4. Reduction in the leaching of chemical nutrients is possible.

Select the correct answer using the code given below:

(a) 1, 2 and 3 only

(b) 1,2 and 4 only

(c) 1,3 and 4 only

(d) 2, 3 and 4 only

Reference:

http://www.fao.org/3/y5053e/y5053e06.htm

Phosphate rock cannot be used as a fertiliser because it is insoluble but it can be used to make fertilisers.

With reference to Ocean Mean Temperature(OMT),which of the following statements is/are correct?

1. OMT is measured upto a depth of 26 degree Celsius isotherm which is 129 meters in the south-western Indian Ocean during January-March.

2. OMT collected during January-March can be used in assessing whether the amount of rainfall in monsoon will be less or more than a certain long-term mean.

Select the correct answer using the code given below:

(a) 1 only

(b) 2 only

(c)Both 1 and 2

(d) Neither 1 nor 2

Reference:

https://www.thehindu.com/sci-tech/science/ocean-mean-temperature-can-better-predict-indian-summer-monsoon/article24842963.ece

The 26 degree C isotherm is seen at depths varying from 50–100 metres. During January–March, the mean 26 degree C isotherm depth in the Southwestern Indian Ocean is 59 metres.

With reference to solar water pumps,consider the following statements: 1. Solar power can be used for running surface pumps and not for submersible pumps. 2. Solar power can be used for running centrifugal pumps and not the ones with piston. Which of the statements given above is/are correct ? (a) 1 only (b) 2 only (c) Both 1 and 2 (d) Neither 1 nor 2

Reference:

https://solarmagazine.com/solar-water-pumps/

https://storage.googleapis.com/e4a-website-assets/Solar-Water-Pump-Technology-Roadmap.pdf

In India,under cyber insurances for individuals,which of the following benefits are generally covered,in addition to payment for the loss of funds and other benefits ?

1. Cost of restoration of the computer system in case of malware disrupting access to one’s computer.

2. Cost of a new computer if some miscreant wilfully damages it,if proved so.

3. Cost of hiring a specialized consultant to minimize the loss in case of cyber extortion.

4. Cost of defence in the court of law if any third party files a suit.

Select the correct answer using the code given below:

(a) 1, 2 and 4 only

(b) 1,3 and 4 only

(c) 2 and 3 only

(d) 1,2,3 and 4

Reference:

https://www.paisabazaar.com/commercial-insurance/cyber-security-insurance/#Types

https://library.educause.edu/~/media/files/library/2017/10/urmiafaq.pdf;Frequently

In Indian context, the standards for cyber insurance are still to be established.

Steel slag can be the material for which of the following?

1. Construction of base road

2. Improvement of agriculture soil

3. Production of cement

Select the correct answer using the given code below

1. 1 and 2 only

2. 2 and 3 only

3. 1 and 3 only

4. 1, 2 and 3

Reference:

https://www.financialexpress.com/market/commodities/steel-slag-may-now-be-used-as-fertiliser-for-soil/1115559/

https://www.sciencedirect.com/topics/engineering/steel-slag

In rural road construction, the use of which of the following is preferred for ensuring environmental sustainability or to reduce carbon footprint?

1. Copper slag

2. Cold mix asphalt technology

3. Geotextiles

4. Hot mix asphalt technology

5. Portland cement

Select the correct answer using the given code below

(a) 1, 2 and 3 only

(b) 2, 3 and 4 only

(c) 4 and 5 only

(d) 1 and 5 only

Reference:

https://niti.gov.in/planningcommission.gov.in/docs/aboutus/committee/wrkgrp12/transport/wgrep_rural.pdf

What is the use of Biochar in farming?

1. Biochar can be used as a part of the growing medium in the vertical farming

2. When biochar is a part of the growing medium, it promotes the growth of nitrogen fixing microorganisms.

3. When biochar is a part of the growing medium, it enables the medium to retain water for a longer time.

Which of the above given statements is/are correct?

(a) 1 and 2 only

(b) 2 only

(c) 1 and 3 only

(d) 1, 2 and 3 only

Reference:

https://www.thehindu.com/business/agri-business/biochar-compost-tea-are-the-new-recipe/article7830057.ece

http://www.nicra-icar.in/nicrarevised/images/Books/Biochor%20Bulletin.pdf

In India, The term “Public Key Infrastructure” is used in the context of?

(a) Digital security infrastructure

(b) Food security infrastructure

(c) Health care and education infrastructure

(d) Telecommunication and transportation infrastructure

Reference:

https://www.isical.ac.in/~palash/talks/PKI-Ind-Iss.pdf