By the time we reach that page we twenty lessons of the book.A. will studyB. will have s

问题补充：

By the time we reach that page, we twenty lessons of the book.

A. will study

B. will have studied

C. would study

D. have studied

答案：

A. will study

(答案→)B. will have studied

C. would study

D. have studied

解析：这题考查时态，时间是：By the time+时间状语从句，“到…时间为止”，主句用相应的过去时，因为时间状语从句用的是一般现在时代替将来时，所以主句用将来完成时。句意是：到我们学到那一页为止，我们将已经学了20课了。选B。