例如：
×To save money, the bus was taken instead of plane.
√To save money, we took the bus instead of plane.
让我们看一道2005年11月份的三级试题：
To succeed in a scientific experiment,______.
A.one needs being patient person.
B.patience is to need.
C.one needs to be patient.
D.patience is what needed.
答案：C
2.不定式的逻辑主语
如要表明不定式或不定式的动作发出者(即逻辑主语)，就要在不定式前用for+名词(或代词的宾格)。如：
Is the road wide enough for two cars to pass?
The conference is too important for you to miss.
3.不定式的时态和语态
不定式有一般、完成、进行等几种常用的形式，也有主动和被动语态的区别。以study为例：
主动/被动一般式to study; to be studied
进行式to be studying
完成式to have studied; to have been studied
1)不定式的时态
不定式的一般式(to do)所表示的动作与谓语动词所表示的动作是同时发生，或是在其后发生的。如：
Thousands of young people are learning to ski.
不定式的进行式(to be doing)所表示的动作与谓语动词的动作是同时进行的，而且是正在进行的。如：
They seemed to be getting along quite well.
不定式的完成进行时(to have done)表示限于谓语动词之前发生的动作或状态，to have + V-ed 表示动作，to have been 表示状态。如：
She seems to have finished her work.
不定式的完成进行时表示动作在谓语动词之前发生，而且一直进行着。如：
She was happy to have been staying with her aunt.
2)不定式的语态
每个不定式都有其逻辑主语，如果逻辑主语是动作的发出者，不定式用主动式，如果其逻辑主语是动作的承受者，不定式用被动式。如：
The doctor recommended him to air the room.
医生建议他打扫房间。
The doctor recommended the room to be aired.
医生建议打扫房间。
考试重点：使用不带to的不定式的几种情况
(1)在口语中，以why开头的简单问句中。例如：
Why do it that way?
Why not go out for a walk?
(2)某些使役动词，如make, let，have等后面跟动词不定时作宾语补足语时，用省略to的不定式。如：
Let him do it.让他做吧。
I would have you know that I am ill.我想要你知道我病了。
(3)表示生理感觉的动词后接不定时作宾语补足语时，不定式不带to.这类词有：
feel 觉得 observe 注意到，看到 hear听到
watch注视 listen to听 perceive察觉，感知
notice注意 see看见 look at看
注意：
表示 "感觉"的动词，既可以用不带to 的不定式作宾语补足语，又可以用现在分词作宾语补足语，但两者有含义上的差别。现在分词作这些动词的宾语补足语，表示动作的进行，以不带to的不定式作这些动词的宾语补足语,表示动作的完成。
例如:
I heard her playing the violin.
我听到她在拉小提琴.
I don't see the ball break the window.
我没有看到球砸坏玻璃.
注意：
上述使役动词与感觉动词转换为被动结构时，其后的不定式需带to，如：
He was seen to come.
The boy was made to go to bed early.
(4)在do nothing/anything/everything but(except)结构中。例如：
Last night I did nothing but watch TV.
昨天晚上，除了看电视，我什么也没干。
但是，如果谓语动词不是"do nothing，anything，everything"，那么but(except)所跟的不定式则仍须带to.
The doctor told him nothing but to stop smoking.
医生除了让他戒烟，其它什么都没有说。
There was nothing for them to do but remain silent.
除了保持沉默以外，他们没有别的办法。
记忆口诀：
前面有do，后面省to，前面无do，后面带to.
(5)下面这些词组是不定式的习惯用法，只能用省to的不定式形式。
can not help but do(不得不)
can not but do(不得不)
cannot choose but do(只能)
have no choice but do (只能)
had better do(最好)
would rather do(宁愿)
例如：
When I consider how talented he is as a painter, I cannot help but believe that the public will appreciate his gift.
责任编辑：mman
