Find out the correct sentence from the following options:

Concept

When a sentence begins with a negative or restrictive adverbial such as "No sooner", English requires subject–auxiliary inversion: the auxiliary verb comes before the subject (had he…, not he had…). The fixed correlative pair is "No sooner … than" (the conjunction is "than", never "then"). Because the first action happens just before the second, the earlier action takes the past perfect (had + past participle) and the later action takes the simple past.

Application

1. Start with the inverted auxiliary after the opening adverbial: "No sooner had he seen me…"

2. Join the two clauses with the correlative conjunction "than": "…than he left the room."

3. Keep the earlier event (seeing) in the past perfect and the later event (leaving) in the simple past.

This gives: "No sooner had he seen me than he left the room."

Contrast

• "No sooner he had seen me than he left the room." — keeps normal subject–verb order (he had) and so omits the required inversion after "No sooner".

• "No sooner had he seen me then he left the room." — has the inversion but uses the adverb "then" (meaning "next") in place of the correlative conjunction "than".

• "No sooner had he seen me than he had left the room." — wrongly puts the later action (leaving) in the past perfect too; the second clause must be simple past.

Result: the sentence with inversion, the conjunction "than", past perfect for the earlier action and simple past for the later action is correct.