My mother used to take a walk after dinner --------------对划线部分提问

问题描述:

My mother used to take a walk after dinner --------------对划线部分提问

这个句子缺状语。严格来说,任何疑问副词都是可以放进去的。
eg:
Where/When/Why did your mother use to take a walk after dinner?

在哪里画的线呢?
①对take a walk 提问的话:What did your mother use to do after dinner?
②对after dinner提问的话:When did your mother use to take a walk?

What did your mother use to do after dinner?

那划线?