i don't know which one to choose.请造几个类似which ...to 的句子

I don't know what to do next
I don;t know which one to buy,the bule one or the white one
could you tell me how to do the work
He did't tell me when to start the game
①Where to go is still a question.
到哪儿去仍然是个问题。（作主语）
②Which to choose is important.
选择哪一个是非常重要的。
③The question is how to learn English well.
问题是怎样才能学好英语。（作表语）
④I know where to find the boy.
我知道在哪里能找到这个男孩。（宾语）
⑤They know what to call it in English.
他们知道用英语叫它什么。（宾语）
⑥Li Ping doesn't know why to learn English.
李平不知道为什么学英语。（宾语）
⑦The doctor told him when to take the medicine.
医生告诉他什么时候服药。（宾语）
.....

i don't know which book to read
i don't know which one to buy
i don't know which bus to take