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

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A. has been pleted
(答案→)B. will have been pleted
C. will plete
D. has pleted
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 e back，故选B，若掌握by the time的用法，就不难了。