Choose the sentence that uses the correct question tag:

The correct answer is Option (1) → Somebody left the tap running in the hostel washroom, didn’t they?

Question tag after “somebody / everyone”:

Words like somebody, someone and everyone take “they” in the tag. “Left” is in the simple past and the sentence is positive. So the tag is “didn’t they”.

Why the Other Options are Incorrect?

Option 2: Kabir works in a bank in Nagpur, isn’t he? — Incorrect. The given sentence says “works ..., isn’t he”. “Works” is a simple present verb with no helping verb. Such a sentence takes “does” in the tag, not “is”.
Corrected: Kabir works in a bank in Nagpur, doesn’t he?

Option 3: The vegetable sellers were late this morning, were they? — Incorrect. The sentence is positive, but the tag is also positive. A positive sentence takes a negative tag.
Corrected: The vegetable sellers were late this morning, weren’t they?

Option 4: Ananya will bring the cake for the party, won’t he? — Incorrect. The tag uses the pronoun for the subject. Ananya is a girl, so the pronoun is “she”, not “he”.
Corrected: Ananya will bring the cake for the party, won’t she?