题目内容：

No sooner_____asleep than she heard a knock at the door
A.she had fallen B.had she fallen C.she fell D.she did fall

优质解答

B
首先这是一个固定句式：no sooner ...than ,意思是,一...就
要注意的是,no sooner 跟过去完成时,than 跟过去式
第二,这里的no 否定词位于句首,因此要倒装,had 提前,因此是B