问题
选择题
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
答案：C
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。
的物质的量浓度（单位mol·L-1）为( )
