If she _______________ how to calibrate the instrument, she _______________ done the experiment. A. knows, will have B. knew, had

GATE 2014 · General Aptitude · Tenses · medium

Answer: B. knew, had

1. Identify the conditional type from context: The sentence implies she did NOT know how to calibrate, so the experiment was NOT done. This is an unreal past condition — a third conditional or past hypothetical.
2. Apply the unreal past conditional structure: Unreal past conditional: [If + past simple (subjunctive)], [would have + past participle] OR equivalently [had + past participle]. Here: 'If she knew ... she had done' fits option B where 'knew' = past subjunctive condition, 'had' (short for 'had done') = past perfect result.
3. Eliminate option A: A. 'knows, will have' — 'knows' is present tense (real condition), 'will have' is future perfect. This would create a first conditional about a real future situation, contradicting the past hypothetical context.