what to do做什么
how to do + 名词/代词 怎么做......
eg. i don't know what to do .我不知道干什么
i don't know how to do it.我不知道怎么干这件事
what to do做什么
how to do怎么做
what to do... 表 干什么...
how to do......表 怎样干...
what to do?做什么?
how to do it? 怎么做?
how to do + it it 做主语
what to do就不用加拉
what to do表示做什么,how to do表示怎么去做。
what to do做什么
how to do怎么做