Task six: 非谓语动词常考的其它结构
疑问词who，what，which，when，where和how后加不定式可构成一种特殊的不定式短语。它在句中可以用作主语、宾语、表语。
例如： When to start has not been decided．
I don't know what to do．
The difficulty was how to cross the river．
I can tell you where to get this book.
请思考：以上句中的不定式短语各在句中做什么成分？
注意: A. 有时疑问词前可用介词，
例如：I have no idea of how to do it. 我不知道如何做此事。
B. 动词know 后面不能直接跟不定式作宾语，只能跟疑问词（how, what）+不定式：
例如：While still a young boy, Tom knew how to play the piano well and as he grew older, he wrote operas, the most famous of which is Carmen.
Ⅱ 介词except和but作“只有…，只能…”讲时跟不定式结构（but与不带to的不定式连用）。
例如：When the streets are full of melting snow, you cannot help but get your shoes wet. 当街上都是融化的雪，你不得不弄湿你的鞋。
I can do nothing but cry. 除了哭，我们什么都做不了。
There was nothing for the enemy to do but surrender. 敌人除了投降什么都做不了了。
注意:如果but或except之前没有do，其后的to 不能省略。
例如：There is no choice but to wait and see.
The enemies had no choice but to surrender.
1) 在表示生理感觉的动词后的不定式不带to。这类词有：
see看见 look at看 watch注视 notice注意 observe 注意到，观察
listen to听 hear听 feel 觉得
例如： I saw her dance yesterday.
His mother often heard him cry.
2）另一类是某些使役动词，如make，let，have等。
例如： 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。
注意:A. 上述感觉动词与使役动词转换为被动结构时．其后的不定式一般需带to
例如： He was seen to come．
The boy was made to go to bed early.
B. 在动词find与help之后，不定式可带to亦可不带to
例如：He was surprised to find the sheep (to) break fence at this season．他发现羊在此季节越出栅栏，感到惊讶。
C. 在do nothing／anything／everything but(except)结构中
例如：Last night I did nothing but watch TV．昨天晚上，我除了看电视别的什么也没有干。
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。
例如：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 to remain silent．除了保持沉默以外，他们没有别的办法。
逻辑主语：是非谓语动词动作的执行者或承受者；它们在逻辑上存在着主谓关系或动宾关系，但不能直接作非谓语动词的主语，因此叫逻辑主语。
1) 不定式的逻辑主语:介词of 或for的宾语就是非谓语动词的逻辑主语。
在表示事物性质，特征等的形容词后面，常用for引出不定式的逻辑主语，此句型结构为：
It's + difficult (easy, hard, important, interesting等）+for 名词/代词.+ to do sth. 即：此句型中for后的名词或代词为不定式的逻辑主语。
例如：It's important for you to learn English well. 学好英语对你非常重要。
It's impossible for him to finish his homework in half an hour. 他在半小时内写完作业是不可能的。
在表示人物性格、特性等的形容词后面，常用of引出不定式的逻辑主语。此句型结构为：
It's + nice(good, kind, considerate, honest, polite, brave/courageous, wise, clever, careless, rude, selfish, stupid, foolish等）+of 名词/代词.+ to do sth. 即：此句型中of后的名词或代词也可以用来表示不定式的逻辑主语。
例如： It is very kind of you to help me．你帮助我太好了。
It was courageous of him to oppose his chief. 他敢反对他的上司，真是勇敢。
It was wise of him to do that．他那样做是明智的。
2)动名词的逻辑主语为：在动名词前用的物主代词或名词所有格。
例如：His coming late made the teacher angry. 他迟到使老师生气了。
Would you mind my opening the door? 我打开窗户你介意吗？
Please excuse my interrupting you. 请原谅我打断你的话。
Mary's going there is of no help. 玛丽去那儿没什么帮助。
Tom insisted on my going with them．他坚持要我和他们一起去。
He dislikes his wife's working late．他不喜欢他妻子工作得很晚。
Would you mind my smoking here? 你介意我在这儿吸烟吗？
在相应的非谓语形式前+not；警示语用No+doing。
例如： We started early in order/so as to not to miss the bus. 为了不误公共汽车，我们出发得早。
He told me not to be late for school. 他告诉我上学不要迟到。
Not knowing how to do it, she asked me for help. 因为不知道怎么做这个事情，她向我求救。
Not having received an answer, I wrote again. 因为没有收到回信，我就又写了一封。
His not going home at night made his mother very worried. 他半夜没回家使他的妈妈很担心。
I regretted not taking your advice. 我很后悔没听你的意见。
Not treated in time, the disease may cause death. 这种病如果不及时治疗就会引起死亡。
No parking here. 此处禁止停车。
No smoking. 禁止吸烟。