求详细过程并分析句子成分?It was announced that only when the fire was un

求详细过程并分析句子成分?It was announced that only when the fire was under control________to ...
求详细过程并分析句子成分?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 residentsbe permitted D．the residents had been permitted