Choose the sentence that uses the correct question tag:

The correct answer is Option (3) → Nothing seems to work on this old laptop, does it?

Question tag after “nothing”:

“Nothing” makes the sentence negative, so the tag is positive. In the tag, “nothing” becomes “it”. “Seems” has no helping verb, so the tag uses “does”.

Why the Other Options are Incorrect?

Option 1: The shopkeeper gave us the wrong change, doesn’t he? — Incorrect. The given sentence says “gave”, which is in the past. “Doesn’t” is present, so the tag must use “didn’t”.
Corrected: The shopkeeper gave us the wrong change, didn’t he?

Option 2: The guard can’t leave his post at night, can’t he? — Incorrect. The sentence has “can’t”, so it is negative. A negative sentence takes a positive tag.
Corrected: The guard can’t leave his post at night, can he?

Option 4: Rohan’s mother teaches maths at our school, doesn’t he? — Incorrect. The tag uses the pronoun for the subject. The subject is “mother”, not “Rohan”. So the pronoun is “she”.
Corrected: Rohan’s mother teaches maths at our school, doesn’t she?