To see is to believe/ To work means to earn a living.
2、另一种情况主语是以aim, duty, hope, idea, happiness, job, plan, problem, purpose, thing, wish等为中心的名词,或以what引导的名词性从句，不定式表语对主语起补充说明作用
His wish is to buy a luxurious car in the near future. / The boss's plan is to start building the skycraper immediately. / What I want to say is to get rid of the plan forever.
11) The function of Louis Sullivan's architecture was providing [A] large uninterrupted floor areas [B] and to allow ample light [C] into the interior [D] .
12) The most important [A] thing is negociate [B] with them about [C] the future of [D] the plant.
3、因为不定式所修饰的名词是不定式的宾语，所以如果不定式动词是不及物动词，那么就要在动词后加上相应的介词He has a lot of trifles to deal with./ I had got no place to live in./That girl has nothing to worry about./the subject to concentrate on. / He has a strict teacher to listen to. / She has four children to look after. / She had a sick mother to live with. / This is the very person to sell your ticket to.
18) Although the lecture had already been on for five minutes, I still was not able to find a chair .
[A] to sit[B] for to sit on[C] to sit on[D] for sitting
4、一些表示企图、努力、倾向、目的、愿望、打算、能力、意向等意义的名词后面要求接不定式作其定语，如：ability, attempt, effort等
19) During [A] the 19th century scientists found [B] that when certain parts of the brain were damaged [C] men lost the ability doing [D] certain things.
20) What is new, however, is the scientific attempt whether other planets beyond our own have given birth to advanced civilizations.
[A] discover[B] discovers[C] discovering[D] to discover
21) Surely her daughter would make an even bigger effort her?
[A] please [B] pleased [C] to please [D] having pleased