．If I too late last night I could not have fallen asleep in class.A. didn’t stay upB. had

问题补充：

．If I too late last night, I could not have fallen asleep in class.

A. didn’t stay up

B. hadn’t stayed up

C. don’t stay up

D. haven’t stayed up

答案：

A. didn’t stay up

(答案→)B. hadn’t stayed up

C. don’t stay up

D. haven’t stayed up

解析：考查if条件状语从句的虚拟语气。If I too late last night是含有if条件状语从句的虚拟语气，根据last night可知是指的过去的事实，要用had done的过去完成时态，所以选B。