Q41easy
Which one of the following is used in preparing a natural mosquito repellent?
(a) Congress grass
(b) Elephant grass
(c) Lemongrass
(d) Nut grass
Answer: (c)
UPSC 2021 Science & Tech PYQ Solved
14 Science & Tech questions from UPSC 2021 Prelims GS Paper 1 — solved with answers
14
Questions
57%
Trap Rate
Common Misconception
Top Trap
Q45easyCommon Misconception
Magnetite particles, suspected to cause neurodegenerative problems, are generated as environmental pollutants from which of the following?
1. Brakes of motor vehicles
2. Engines of motor vehicles
3. Microwave stoves within homes
4. Power plants
5. Telephone lines
Select the correct answer using the code given below.
(a) 1, 2, 3 and 5 only
(b) 1, 2 and 4 only
(c) 3, 4 and 5 only
(d) 1, 2, 3, 4 and 5
Answer: (d)
Trap: Common Misconception
Telephone lines and microwave stoves generating magnetite particles seems implausible, making students exclude 3 and 5 and pick (b). However, research shows magnetite nanoparticles are generated from various sources including electrical equipment and heating devices. The 'all of the above' seems counterintuitive.
Q75moderateAbsolute Qualifier
With reference to recent developments regarding 'Recombinant Vector Vaccines', consider the following statements :
1. Genetic engineering is applied in the development of these vaccines.
2. Bacteria and viruses are used as vectors.
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
Answer: (c)
Trap: Absolute Qualifier
Students might think only viruses are used as vectors (like adenovirus in Oxford-AstraZeneca vaccine) and exclude bacteria. But bacteria like Salmonella and Listeria can also be used as recombinant vectors in vaccine development. The trap is in the assumption that 'vector' only means viral vector.
Q76moderatePartial Truth
In the context of hereditary diseases, consider the following statements :
1. Passing on mitochondrial diseases from parent to child can be prevented by mitochondrial replacement therapy either before or after in vitro fertilization of egg.
2. A child inherits mitochondrial diseases entirely from mother and not from father.
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
Answer: (c)
Trap: Partial Truth
Students might doubt statement 1 because 'either before or after IVF' sounds too broad. MRT can indeed be done both ways - maternal spindle transfer (before fertilization) and pronuclear transfer (after fertilization). Statement 2 about maternal inheritance of mitochondria is standard biology. The doubt about timing in statement 1 is the trap.
Q77easy
Bollgard I and Bollgard II technologies are mentioned in the context of
(a) clonal propagation of crop plants
(b) developing genetically modified crop plants
(c) production of plant growth substances
(d) production of biofertilizers
Answer: (b)
Q78moderateCommon Misconception
In a pressure cooker, the temperature at which the food is cooked depends mainly upon which of the following?
1. Area of the hole in the lid
2. Temperature of the flame
3. Weight of the lid
Select the correct answer using the code given below.
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer: (d)
Trap: Common Misconception
Students might think the temperature of the flame doesn't matter once pressure builds up (thinking only pressure determines cooking temperature). But the flame temperature determines the rate of heat input and thus the equilibrium temperature and pressure inside. The hole area determines steam escape rate, and lid weight determines the pressure threshold.
Q79easy
Consider the following :
1. Bacteria
2. Fungi
3. Virus
Which of the above can be cultured in artificial/synthetic medium?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer: (a)
Q80moderateCommon Misconception
Consider the following statements :
1. Adenoviruses have single-stranded DNA genomes whereas retroviruses have double-stranded DNA genomes.
2. Common cold is sometime caused by an adenovirus whereas AIDS is caused by a retrovirus.
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
Answer: (b)
Trap: Common Misconception
Statement 1 is the trap with reversed facts. Adenoviruses have DOUBLE-stranded DNA (not single), and retroviruses have single-stranded RNA (not double-stranded DNA). The statement swaps the genome types. Students with partial knowledge might accept this because they remember 'DNA' for adenovirus and 'different' for retrovirus.
Q91easy
Water can dissolve more substances than any other liquid because
(a) it is dipolar in nature
(b) it is a good conductor of heat
(c) it has high value of specific heat
(d) it is an oxide of hydrogen
Answer: (a)
Q92moderateCommon Misconception
With reference to street-lighting, how do sodium lamps differ from LED lamps?
1. Sodium lamps produce light in 360 degrees but it is not so in the case of LED lamps.
2. As street-lights, sodium lamps have longer life span than LED lamps.
3. The spectrum of visible light from sodium lamps is almost monochromatic while LED lamps offer significant colour advantages in street-lighting.
Select the correct answer using the code given below.
(a) 3 only
(b) 2 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer: (c)
Trap: Common Misconception
Statement 2 is the trap. Students might think traditional sodium lamps, being robust old technology, last longer. But LED lamps actually have a LONGER lifespan (50,000-100,000 hours) compared to sodium lamps (12,000-24,000 hours). The 'old technology = durable' assumption misleads.
Q93easy
The term 'ACE2' is talked about in the context of
(a) genes introduced in the genetically modified plants
(b) development of India's own satellite navigation system
(c) radio collars for wildlife tracking
(d) spread of viral diseases
Answer: (d)
Q94moderateSimilar Sounding
Bisphenol A (BPA), a cause of concern, is a structural/key component in the manufacture of which of the following kinds of plastics?
(a) Low-density polyethylene
(b) Polycarbonate
(c) Polyethylene terephthalate
(d) Polyvinyl chloride
Answer: (b)
Trap: Similar Sounding
Option (c) PET is a common plastic associated with food/beverage containers, and students might link BPA concerns (which are about food contact materials) to PET. But BPA is a monomer specifically used in making polycarbonate plastics and epoxy resins. PET does not contain BPA.
Q95moderateDistractor Pairing
'Triclosan', considered harmful when exposed to high levels for a long time, is most likely present in which of the following?
(a) Food preservatives
(b) Fruit-ripening substances
(c) Reused plastic containers
(d) Toiletries
Answer: (d)
Trap: Distractor Pairing
Option (a) food preservatives and option (c) reused plastic containers are tempting because they also involve chemical exposure concerns. But Triclosan is specifically an antibacterial/antimicrobial agent used in soaps, toothpaste, deodorants, and other toiletries/personal care products.
Q96easy
Which one of the following is a reason why astronomical distances are measured in light-years?
(a) Distances among stellar bodies do not change.
(b) Gravity of stellar bodies does not change.
(c) Light always travels in straight line.
(d) Speed of light is always same.
Answer: (d)