What ___ your mother often do when it __?

What ___ your mother often do when it __?
A.does,rains
B.does,is raining
C.do,rains
我的第一感觉是A,
但是书上有一个句子:What do you usually do when it's raining?
因此,有点困惑,希望大家帮小女子解惑!