---What will you do if it_____ tomorrow?

题目

---What will you do if it_____ tomorrow?
---I'll stay with my grandmother and have a chat.
A.will rain B.rains
C.is rain D.rain
正确答案是B,为什么其他3个不行?

答案

if 引导的条件状语从句,主句用一般将来时,从句用一般现在时,
e.g I will not go to the garden if it rains tomorrow .