Look out! The ceiling l down. A. is to fallB. will fallC. is going to fallD. is falling

问题补充：

Look out! The ceiling l down.

A. is to fall

B. will fall

C. is going to fall

D. is falling

答案：

A. is to fall

B. will fall

(答案→)C. is going to fall

D. is falling

解析：通过“Look out! ”可知房顶将要掉下来，而且是根据某种迹象表明要发生某事，应该使用be going to ，使用答案C。