You should ___________ when to say _______________. A. no / no B. no / know C. know / know D. know / no

GATE 2022 · General Aptitude · Most Appropriate Word · medium

Answer: D. know / no

1. Analyse blank 1: 'You should ___ when to say ___': After 'You should', a base-form verb is required. 'Know' fits perfectly: 'You should know when...' means 'you ought to be aware of when...' The word 'no' cannot function as a verb here.
2. Analyse blank 2: '...when to say ___': The phrase 'when to say ___' asks what word is uttered as a refusal. One 'says no' to decline. The word 'know' cannot be 'said' in this context — 'when to say know' is meaningless.
3. Confirm option D: know / no: 'You should know when to say no.' — This is a complete, idiomatic English sentence conveying the importance of recognising the right moment to refuse or decline. Option D (know / no) is correct.