问题补充：
The plane couldn’t take off on time the heavy rain.
A. because
B. so that
C. because of
D. as
答案：
A. because
B. so that
(答案→)C. because of
D. as
解析：句意：由于大雨飞机不能按时起飞。A. because因为，后跟从句；B. so that如此……以至于……C. because of 因为，后跟名词或短语；D. as由于,后跟从句，一般放在句首，语气较弱，较口语化。结合语境可知选C.
