Select the most appropriate option to substitute the underlined segment in the given sentence. Rohan exercised and ate a lot, lest he should not be weak .

Correct — A. Lest already carries the negative. It means for fear that, so the clause after it is written positively.

Adding not doubles the negative and reverses the sense: lest he should not be weak would say he exercised for fear of not being weak.

Lest is also followed by should plus the base verb, or by the bare subjunctive be, never by would.

Lest he should be weak obeys both rules, so option (a).

Why the others are wrong

• (b)
  lest he should not weak — Keeps the surplus not and also loses the verb. Should not weak has no be, so the clause has no predicate at all.
• (c)
  lest he would be weak — Would does not follow lest. The conjunction takes should, or the bare subjunctive form: lest he be weak.
• (d)
  lest he would not be weak. — Carries both faults at once: would after lest, and the not that lest has already supplied.

Lest is a negative subordinating conjunction. It means for fear that, or in order that something should not happen, so the negation is built into the word itself.

Two rules follow, and this item tests both.

Never put not inside a lest-clause. Lest he should fall is correct; lest he should not fall says the opposite of what is meant.

Use should after lest, or the bare subjunctive. Lest he should be weak and lest he be weak are both standard, while lest he would be weak is not.

Key facts

• Lest means for fear that and is negative in itself, so no not follows it.
• Lest is followed by should plus the base verb, or by the bare subjunctive: lest he be weak.
• Unless carries the same built-in negative, which is why unless you do not is wrong.

Common traps

• Keeping not because the sentence seems to mean he did not want to be weak.
• Swapping should for would, which sounds natural elsewhere but is wrong after lest.

No directly related past PYQ was found.