The teacher asked the students to hand in their papers when they

The teacher asked the students to hand in their papers when they________ the test.
A、had finished
B、would finish
C、would have finished
D、were finishing
【正确答案】：A
【题目解析】：原句的意思是“老师让学生们写完试卷就交卷。”这里The teacher asked是一个一般过去时，when they have finish the test是一个现在完成时，即“当他们已经完成测试的时候”。由于状语从句when they have finish the test受到主句过去时态的制约The teacher asked，所以就要从现在完成时变成过去完成时when they had finish the test。因此选择A. had finished。