UPSC Prelims 2025 · GS Paper I
Question 49: Science and Technology
Consider the following statements :
- INo virus can survive in ocean waters.
- IINo virus can infect bacteria.
- IIINo virus can change the cellular transcriptional activity in host cells.
How many of the statements given above are correct?
AnswerThe answer is (d).
Viruses are the most abundant biological entities in the oceans, with enormous numbers in every litre of seawater, so Statement I is wrong. Bacteriophages are viruses that infect bacteria, so Statement II is wrong. Many viruses take over the host cell and change its gene expression, or transcription, to make copies of themselves, so Statement III is wrong. None of the three is correct.
- I. Viruses are abundant in ocean waters.
- II. Bacteriophages infect bacteria.
- III. Viruses commonly alter the transcription of host cells.
How you could have got this
No shortcut here: in a “how many” question, ruling out options doesn’t help. Every statement has to be judged.
This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.
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) Wrong: none of the three statements is correct.
- (b) Wrong: none of the three statements is correct.
- (c) Wrong: all three statements are false.
- (d) Right: ocean viruses, bacteriophages and host-gene takeover all contradict the statements.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2025, General Studies Paper I, Series A. The paper on upsc.gov.in.