一道选择题I wonder_____

I wonder what to do next

A.how to do B.what to do C.what to do next D.how to do next
what to do==how to do it 是固定 结构。
我是从事英语的，不明再问啦。

C

我想知道下一步做什么。
what to do==how to do it

C 如果是D要说how to do it next

个人倾向于C,纯属语感...

选C语感啊