2021 CSAT, all questions

UPSC Prelims 2021 · CSAT

Question 4: Reading Comprehension

Passage – 4 · as printed by UPSC
Passage beginning “Researchers were able to use stem…”

On the basis of the passage given above, the following assumptions have been made :

  1. 1.BPA may alter embryonic development in vivo.
  2. 2.Biochemical and cell-based assays are useful in finding out treatments for pollution-induced diseases.
  3. 3.Embryonic stem cells could serve as a model to evaluate the physiological effects of environmental pollutants.

Which of the above assumptions are valid ?

a1 and 2 only
b2 and 3 only
c1 and 3 only
d1, 2 and 3

AnswerUPSC’s answer is (c).

Test each assumption against what the study did. Mouse embryonic stem cells were treated with BPA, and its toxic effect on early cell layers and nerve precursor cells was measured; BPA is also said to cause developmental abnormalities in humans. So BPA can plausibly disturb embryonic development (1), and stem cells can model a pollutant's effects on the body (3). The assays were used to detect and measure toxicity, not to find treatments, so 2 goes beyond the passage. Remember: be wary of assumptions that jump from detecting harm to curing it.

  • 1. BPA disturbed early cell specialisation in the stem cells and is linked to developmental abnormalities in people, so it may alter embryonic development in the body.
  • 2. The assays measured BPA's toxicity; finding treatments is not mentioned.
  • 3. The researchers used embryonic stem cells to gauge BPA's effects, showing they can serve as a model.

How you could have got this

  1. If you were sure statement 2 is not correct, (a), (b) and (d) go: each of them includes 2.

    What you needed to know: The assays measured BPA's toxicity; finding treatments is not mentioned.

Only (c) is left. You didn’t need statements 1 or 3.

Which options go is worked out from UPSC’s key and the options, not by a model.

Why each option is right or wrong
  • (a) Pairs the valid 1 with 2, but 2 is about finding treatments, which the study never attempted.
  • (b) Pairs the valid 3 with 2, which fails for the same reason, and drops the valid 1.
  • (c) Right: 1 and 3 both follow from the study's findings and method.
  • (d) Includes 2, which overreaches; the assays measured toxicity and did not look for treatments.

Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2021, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.