e.g: To finish the building in a month is difficult.
To do such things is foolish.
To see is to believe. (对等)
注: 1). 不定式作主语时,宾语用奇数
(1)It is/was adj. of sb. to do…
(2) It is adj. for sb. to do…
It is easy / difficult / hard / foolish / unwise / right / wrong / unnecessary
(3) it is a 专有名词 to do...
It is a pity / a pleasure / a pleasant thing / one’s duty / an honor / a shame / a crime / no easy job… to do
It takes (sb.) some time / courage / patience …to do…
It requires courage / patience / hard work… to do…
*留意: probable 和 possible 均可作表语，但possible可以用不定式作真正主语， 而probable不能用不定式作真正主语。
It is probable for him to come to the meeting.(错)
It is possible for him to come to the meeting.
It is possible / probable that he will come to the meeting.
主语是以aim duty hope idea intention plan job suggestion wish purpose task 等为中心语的名词词组 或以 what 正确引导的名词性从句表明，后边的不定式表明其內容, 不定式作表语常表明未来或如今的动作或情况。
eg :My idea is to climb the mountain from the north.
Your mistake was not to write that letter.
What I would suggest is to start work at once.
ask, agree, care, choose, demand, decide, expect, fail, help, hope, learn, manage, offer, plan, prepare, pretend, promise, rlikeabcuse, want, wish等只有用形容词不定式作宾语
要想学习培训 早准备( want learn plan)
快提前准备 有期待( prepare hope wish expect)
愿意否 提供选择(agree offer choose)
决策了 已同意(decide be determined promise)
竭尽全力去 下手做(manage undertake)
别回绝 别装作(rlikeabcuse pretend)
e.g.Tom rlikeabcused to lend me his pen.
We hope to get there blikeabcore dark.
The girl decided to do it herself.
stop go on remember forget
regret try mean can’t help
be used to
She found the door broken in when she came back.(宾补与宾语有处于被动的关联，表一种情况。)
Eg:They kept the door locked for a long time.
Keep your mouth shut and your eyes open.(俗语：少说多看看)
Don't leave such an important thing undone.
Don't leave the windows broken like this all the time.
1.留意“have 宾语 过去分词”的二种状况：
eg: I have had my bike repaired.
The villagers had many trees planted just then.
Eg:I had my wallet stolen on a bus last month.
The old man had his leg broken in the accident.
He had his leg broken in the match yesterday.(MET1986)
2."make 宾语 过去分词",在这类构造中，过去分词的形容词务必是表明結果含意的。如：
They managed to make themselves understood in very simple English.
I raised my voice to make myself heard.
三、过去分词用在感官形容词watch,notice,see,hear,listen to ,feel,find等后边。如
When we got to school,we saw the door locked.
We can hear the windows beaten by the heavy rain drops.
He felt himself cheated.
The managers discussed the plan that they would like to see carried out the next year.(NMET2000)
The boss wouldn't like the problem discussed at the moment.
I would like my house painted white.
I want the suit made to his own measure.
I wish the problem settled.
五、过去分词用在“with 宾语 宾补”这一构造中，过去分词与宾语中间是动宾关系。如：
The thilikeabc was brought in with his hands tied behind his back.
With many brightly-coloured flowers planted around the building ,his house looks like a beautiful garden.
With everything well arranged,he llikeabct the office.
eg:He didn't notice me waiting.
I heard the song sung in English.
I saw him opening the window.
I saw the window opened.
I saw him open the window.
I heard her sing the song in English.