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

芯线焊接时，焊点应（）。

A.越大越好

B.光滑

C.平坦

D.圆满

E.不成瘤型

F.可成瘤型