这些动词包括：help, tell, want, would like, expect, need, mean, would prefer, persuade, cause, encourage.
例：Will you help me to pack?
使用情景2：某些介词动词+宾语+不定式。如wait for, arrange for
例：Can you wait for me to finish checking my mail?
I arranged for the students to have meal in the canteen.
主语+不定式（for sb. to do）
例：The plan was for John to buy a bus.
例：It's important for there to be a fire escape at the back of the building.
名词/代词+不定式（sth. to do）
例：I've got some phone calls to make.
Have you got enough to drink？
There's too much work to do.
例：I wish the children had a garden to play in.
I need somebody to talk to.
例：a garden in which to play
4.可用带 for 的结构显示不定式的主语。
例：Here are some documents for Mary to sign.
形容词+不定式（easy to do）
例：His lectures are easy to understand. It's too heavy to carry.
例：She's nice to talk to. Some things are hard to think about.