The task by the time you come back.A. has been completedB. will have been completedC. wil

问题补充：

The task by the time you come back.

A. has been completed

B. will have been completed

C. will complete

D. has completed

答案：

A. has been completed

(答案→)B. will have been completed

C. will complete

D. has completed

解析： 此题考查时间状语从句。by the time+一般现在时态，主句应用将来完成时态，by the time+一般过去时态，主句应用过去完成时态，题中by the time后面是一般现在时态you come back，故选B，若掌握by the time的用法，就不难了。