你好,
动词不定式短语代替宾语从句时,经常和疑问词连用.
eg.1.I didn't know what I could do. =I didn't know what to do.
2.She hasn't decided where she will go.=She hasn't decided where to go.
3.They want to know when they will leave.=They want to know when to leave.
4.He doesn't know how he can get to the park.
=He doesn't know how to get to the park.
5.Jim didn't decide which coat he should buy.=Jim didn't decide which coat to buy.
希望能帮到你,祝你开心.