SomepassengerswerewalkingthroughoneofthebighallsatParis...

問題詳情：

Some passengers were walking through one of the big halls at Paris' Charles De Gaulle Airport __    the whole roof(屋頂)fell down.  

A. while                B. as soon as                     C. when                      D. after

【回答】

C

解析：依據題結構，be doing sth…when…表示“正在……這時……”的意思。故選C。

知識點：連詞

題型：選擇題