Question

Look at the _____!It's_____heavily now. A.rian;rains B.rain;raining C.rains;rainy D.rain;rains

Answer 1

B.rain;raining
与不可数，所以不加S
now现在进行时，所以rainning

Answer 2

B 看看雨 正在下很大

Answer 3

B 雨是不可数名词，所以不能用复数；后一个空要用现在进行时，根据语境Look at 和now 可以判断。