动词不定式的特殊用法（1），赶快记住这些特殊用法吧！

1.It's for sb.和It's of sb.
1）for sb.常用于表示事物的特征特点，表示客观形式的形容词，如easy,hard,difficult,interesting,impossible等：
It's very hard for him to study two languages.对他来说学两门外语是很难的。
2）of sb的句型一般用表示人物的性格，品德，表示主观感情或态度的形容词，如good,kind,nice,clever,foolish,right。
It's very nice of you to help me.你来帮助我，你真是太好了。
for与of的辨别方法：用介词后面的代词作主语，用介词前边的形容词作表语，造个句子。如果道理上通顺用of，不通则用for。如：
You are nice.(通顺，所以应用of)。
He is hard.(人是困难的，不通，因此应用for。)
2.用作介词的to
to有两种用法：一为不定式+动词原形；一为介词+名词/动名词,to在下面的用法中是第二种，即to+名词/动名词：
admit to承认，confess to承认，be accustomed to习惯于，be used to习惯于，stick to坚持，turn to开始，着手于，devote oneself to献身于，be devoted to致力于，look forward to盼望，pay attention to注意
3.省to的动词不定式
1）情态动词(除ought外，ought to)：
2）使役动词let,have,make：
3）感官动词see,watch,look at,notice,observe,hear,listen to,smell,feel,find等后作宾补，省略to。
注意：在被动语态中则to不能省掉。
I saw him dance.
=He was seen to dance.
The boss made them work the whole night.
=They were made to work the whole night.
4）would rather，had better：
5）Why…/why not…：
6）help可带to，也可不带to,help sb(to)do sth：
7）but和except：but前是动词do时，后面出现的动词用不带to的动词不定式。
8）由and,or和than连接的两个不定式，第二个to可以省去：
9）通常在discover,imagine,suppose,think,understand等词后，可以省去to be：
He is supposed(to be)nice.他应该是个好人。
举例：
He wants to move to France and marry the girl.
He wants to do nothing but go out.
比较：
He wants to do nothing but go out.
He wants to believe anything but to take the medicine.
典型例题
1)----I usually go there by train.
----Why not ___ by boat for a change?
A.to try going B.trying to go C.to try and go D.try going
答案：D.why not后面接不带to的不定式，因此选D。
2）Paul doesn't have to be made ___.He always works hard.
A.learn B.to learn C.learned D.learning
答案：B.make后接不带to的动词不定式，当其用于被动时，to不可省略。