No sooner themselves in their seats in the hall than the speaker began his speech.A. they

问题补充：

No sooner themselves in their seats in the hall than the speaker began his speech.

A. they settled

B. had they settled

C. did they settle

D. they had settled

答案：

A. they settled

(答案→)B. had they settled

C. did they settle

D. they had settled

解析：句意：他们一在座位上坐下，演讲者就开始他的演讲。no sooner…than…,hardly…when…结构中，主句应用过去完成时的倒装结构。故选B。