Choose the sentence that uses the correct question tag:

The correct answer is Option (3) → No one called while I was at the bank, did they?

Question tag after “no one”:

“No one” makes the sentence negative, so the tag is positive. In the tag, “no one” becomes “they”. “Called” has no helping verb, so the tag uses “did”.

Why the Other Options are Incorrect?

Option 1: The peon has locked the staff room, isn’t he? — Incorrect. The helping verb in the sentence is “has”. The tag must repeat “has”, not use “is”.
Corrected: The peon has locked the staff room, hasn’t he?

Option 2: Rahul and Imran didn’t book the cab, didn’t they? — Incorrect. The sentence has “didn’t”, so it is negative. A negative sentence takes a positive tag.
Corrected: Rahul and Imran didn’t book the cab, did they?

Option 4: The cricket match was called off due to rain, wasn’t they? — Incorrect. The tag uses the pronoun for the subject. “The cricket match” is one thing, so the pronoun is “it”.
Corrected: The cricket match was called off due to rain, wasn’t it?