．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
网友回答
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。