Iwon’ttellthestudenttheanswertothemathproblemuntilhe  ...

问题详情：

 I won’t tell the student the answer to the math problem until he        on it for more than an hour.

A. has been working                       B. will have worked   

C. will have been working                  D. had worked                              

【回答】

A

知识点：现在完成进行时及其被动式

题型：选择题