Rain is pouring down from the sky without any sign of stopping．Farmers begin to worry about their crops since it as long as 24 hours．
A. would rain
B. had rained
C. was raining
D. has been raining
网友回答
A. would rain
B. had rained
C. was raining
(答案→)D. has been raining
解析：考查时态。句意：雨水从天空倾盆而下，没有一点停的迹象。由于雨一直不停的下了24个小时了，农民们开始担心他们的庄稼。结合语境可知下文描述的是现在已经完成的正在进行的动作，故用完成进行时，选D。