GATE CSE 2014 Set 3 | Question: GA-2

Question

If she _______________ how to calibrate the instrument, she _______________ done the experiment.

• A. knows, will have
• B. knew, had
• C. had known, could have
• D. should have known, would have

Answer 1

The correct answer is:

Had known, could have

Here's why:

• The sentence is in the third conditional which deals with hypothetical situations in the past that did not happen.
• "Had known" is the past perfect tense of "know" and indicates a completed action in the past that would have had an impact on the present.
• "Could have" is the past modal of "can" and expresses possibility or ability in the past that was not realized due to the hypothetical condition not met.

Therefore, if she had known how to calibrate the instrument in the past (hypothetical situation), she would have been able to do the experiment in the past (unrealized possibility).

The other options are incorrect because:

• "Knows, will have" is in the present tense and future tense, and doesn't refer to a hypothetical situation in the past.
• "Knew, had" is in the past tense but doesn't express the unrealized possibility in the past.
• "Should have known, would have" implies obligation or moral judgment, which is not present in the given sentence.

I hope this explanation helps!