Aonther two months will be needed before the new bridge ____.D

问题描述:

Aonther two months will be needed before the new bridge ____.D
Aonther two months will be needed before the new bridge ____.A.completes
B.is completed
C.has completed
D.will be completed
为什么是主将从现

B因为桥是被建完用被动,before 引导时间状语从句,用一般现在是表示将来