动词不定式的很有趣的用法。 它可以和特殊疑问词连用

如：

We can use a question word with a to-infinitive after a verb.

I don't know what to do now.

特殊疑问词+ to do/be 的用法：

1. 作宾语

有些及物动词的后面可以直接放上特殊疑问词+ 不定式来做宾语。

比如：

know what to do

ask when to leave

find where to ask for help

例句：

（1）Daniel did not say who to talk to about this book?

（2）Kitty cannot decide which to choose first.

（3）Sandy is wondering where to ask for help.

（4）Amy does not know how to write the report.

2. 作宾语补足语

可以跟在一个宾语后面来补充说明这个宾语一些情况， 这种成分成为宾语补足语，简称宾补。

例：

（1）Mr Wu advised us which to choose as after-school activities.

（2）The students asked their teacher when to hand in their work.

（3）Millie showed us what to do next.

（4）Daniel taught himself how to use a computer to draw.