Choose the sentence that uses the correct question tag:

The correct answer is Option (2) → Mr Sharma was unhappy with the loud music last night, wasn’t he?

Question tag after a word with “un-”:

A word like “unhappy” has a negative meaning, but it does not make the sentence negative. Words like “not”, “never” or “few” do that. So the sentence is positive and takes the negative tag “wasn’t he”.

Why the Other Options are Incorrect?

Option 1: Sunil seldom eats outside food, doesn’t he? — Incorrect. The given sentence has “seldom”, which makes it negative. A negative sentence takes a positive tag.
Corrected: Sunil seldom eats outside food, does he?

Option 3: Let’s buy some jalebis on the way home, will we? — Incorrect. A sentence that begins with “Let’s” always takes “shall we”.
Corrected: Let’s buy some jalebis on the way home, shall we?

Option 4: The new watchman locks the gate at ten, doesn’t she? — Incorrect. The tag uses the pronoun for the subject. A watchman is a man, so the pronoun is “he”.
Corrected: The new watchman locks the gate at ten, doesn’t he?