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
D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。