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 the residents be permitted
D. the residents had been permitted
答案：
A. the residents would be permitted
B. had the residents been permitted
(答案→)C. would the residents be permitted
D. the residents had been permitted
解析：考查倒装。that从句中only引导的时间状语从句位于句首，其主句需用部分倒装结构。句意：据宣布，只有在火势被控制住的时候居民们才被允许回到家中。
