The accident occurred when the passengers . . . . . . . .

A. sleep

B. had slept

C. had been sleeping

D. were sleeping

Answer: Option D

Solution(By Examveda Team)

The sentence is in past continuous. We use was/were + the -ing form of the verb. We generally use the past continuous to talk about actions and states in progress (happening) around a particular time in the past. It can emphasize that the action or state continued for a period of time in the past.