Since the road is wet this morning, last night.
A. it must rain
B. it must be raining
C. it must have rained
D. it must have been rain
网友回答
A. it must rain
B. it must be raining
(答案→)C. it must have rained
D. it must have been rain
解析： must have done用于对过去发生的事情进行推测，且较有把握。