It heavily when he got back home for he was wet all over．
A. was raining
B. must have been raining
C. must be raining
D. rained
网友回答
A. was raining
(答案→)B. must have been raining
C. must be raining
D. rained
解析：本题考查时态。when 从句表示正在发生的动作。must have been raining表示过去一直在延续的动作，符合题意。选B。