SomepassengerswerewalkingthroughoneofthebighallsatParis...

问题详情：

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

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

【回答】

C

解析：依据题结构，be doing sth…when…表示“正在……这时……”的意思。故选C。

知识点：连词

题型：选择题