问题补充：
It was announced that only when the fire was under control to return to their homes.
A. the residents would be permitted
B. had the residents been permitted
C. would be residents be permitted
D. the residents had been permitted
答案：
A. the residents would be permitted
B. had the residents been permitted
C. would be residents be permitted
D. the residents had been permitted
解析：本题既考查虚拟语气又考查倒装句的用法，本题关键在句子后半部分，前面it 做形式主语，that 引导的真正主句当中又是以only +时间状语位于句首，所以主句要部分倒装。
