See the clouds! It rain.A. willB. is going toC. mustD. certainly

问题补充：

See the clouds! It rain.

A. will

B. is going to

C. must

D. certainly

答案：

A. will

(答案→)B. is going to

C. must

D. certainly

解析：表示马上要发生或打算要做的事用be going to,不用 will,后者主要表示将来的事或表意愿.