Select the most appropriate option to improve the bold part of the sentence.
It is high time you leave the room.

Correct option is C

The correct substitution of the highlighted words is (c) left the room.
Explanation: After expressions like “It is (high/about) time + subject”, we commonly use the simple past to express a present/urgent necessity. Thus, “It is high time you left the room” means you should leave now. Using present (“leave”) is non-standard in this idiom; present perfect (“have left”) or past perfect (“had left”) misrepresent time reference.
Grammatical rule used:
· Pattern: It is (high/about) time + S + V₂ (simple past) to suggest something is overdue now.
· Alternative pattern: It’s time to + V₁ (no subject change): “It’s time to leave.”
· Example:
· “It’s high time we started the meeting.” (= we should start now)
· “It’s time to submit the assignment.”
· Information booster (exceptions/notes):
· Formal/British English prefers the past form after It’s (high) time.
· With “for + noun/pronoun + to-infinitive”: “It’s time for you to leave.”
· Why the other options are wrong:
· (a) have left → Present perfect doesn’t fit the idiomatic structure and implies completed action before now.
· (b) had left → Past perfect requires a past reference point; here we express a present urgency.
· (d) leaves → Third-person singular present; subject is you, and the idiom requires past form.