点击动词不定式作主语时的五个注意:不定式
时间：2019-01-30 03:36:55 来源：柠檬阅读网 本文已影响 人 
编者按:语法是初中英语学习的重要内容。抓住大的语法项目,有助于构建英语知识网络,提高英语语言技能。在此,我们邀请经验丰富的一线老师就九年级牛津英语教材的语法重点,结合各类测试中常见的考点进行剖析,并精心编制专项练习供同学们“练兵”,敬请留意。
在9A第一单元中,同学们已学习了动词不定式在句中充当主语的用法,掌握这一知识点时一定要注意以下五点:
一、注意主谓一致
①单个动词不定式作主语时,谓语动词用单数。例如:
To learn a foreign language well is difficult.
要学好一门外语是有难度的。
②如果and连接两个或更多并列的不定式作主语,被并列的不定式语义一致或基本一致时,谓语动词用单数;如果不一致,谓语动词用复数。例如:
To love and to be loved is sweet to us.
爱或被爱对我们来说都是甜蜜的。
To improve people’s lives and to speed up socialist construction are our two important tasks today.
提高人民生活水平,加快社会主义建设是我们今天的两项重要任务。
二、注意句子的平衡
不定式或不定式短语作主语时,可以直接位于句首。当不定式短语较长时,为保持句子平衡,通常用it作形式主语,而将真正的主语――动词不定式短语放在句子的后面。其常用的句式有:①“It + be + adj.(for/of sb/sth)+ to do sth.”;② “It takes +sb. + some time + to do sth.”。例如:
To drive in the mountains is very difficult.
→It’s very difficult to drive in the mountains.
To do my homework takes me half an hour every day.
→It takes me half an hour to do my homework every day.
三、注意动词不定式作主语的疑问句或感叹句
如果疑问句或感叹句的主语是动词不定式,通常用it作形式主语。试体会:
在英国靠左行驶正确吗?
[误]Is to drive on the left in Britain right?
[正]Is it right to drive on the left in Britain?
今晚能看到一场精彩的足球赛是多么令人激动啊!
[误]How exciting to watch a wonderful football match tonight!
[正]How exciting it is to watch a wonderful football match tonight!
四、注意of与for的正确选用
“It +be +adj+ for/ of + sb. /sth. to do sth.”句型中,of与for的正确选用既是语法难点,也是各类测试命题的热点。一般说来,be后面接名词或接表示事物性质的形容词(如easy, difficult, important等)时,常用介词for; 如果be后面接指人的性情或特征的形容词(如clever, kind, foolish等),一般用介词of。例如:
It’s difficult for him to give up smoking.
It’s very kind of you to help me.
由于“It +be +adj+ of sb. /sth. +to do sth.”这一句型中,不定式的逻辑主语可以转换为句子的主语,而“It +be +adj+ for + sb. /sth. to do sth.”这一句型不可以作这种转换,由此,同学们可以运用以下方法来快速判断是选of还是for:把介词(for或of)后的宾语变成新句子中的主语,然后再接be动词及动词不定式等,如果新构成的句子在句意上讲得通,则用of;反之用for。例如:
It’s very kind(for/of) you to help me look after my baby.
[简析]首先把试题变成:You are (very) kind to help me look after my baby. 接着翻译该句,可以发现句意通顺,故可判断of是正确答案。
[友情提醒]of和for都是介词,如后接代词作宾语,要用宾格代词。试体会:
我们在足球赛前和赛中互相支持、互相帮助是很有必要的。
[误]It’s necessary for we to support and help each other both before and during the football match.
[正]It’s necessary for us to support and help each other both before and during the football match.
五、注意与动名词作主语的区别
动名词与动词不定式均可作主语。一般来说,动名词表示一贯的动作或抽象的概念,或泛指某个已过去的动作,时间概念不强或不明显;而不定式往往是具体的或特定的动作,或指现在或将来的某个未完成的动作。
试对比:
Taking a walk after supper is good for your health.
晚饭后散步对健康有益。
To take a walk after supper this evening is a good idea.
今晚晚餐后去散步是个好主意。
针对练习
单项选择,选择最佳答案。
1. Is it impossiblehimthe problem?
A. of;solveB. for;solveC. of;to solveD. for;to solve
2. ―It’s not difficult for us Chinese well.
―That’s right. Practice makes perfect.
A. to learnB. learningC. learnedD. learn
3. It’s wrongnother an e-mail.
A. for you;postB. for me;readingC. of him;sendingD. of you;to send
4. It them three hoursthe faraway village last Sunday.
A. takes;to get toB. takes;get toC. took;to get toD. took;get to
5.to leave the beautiful park so early!
A. What a pity is itB. How a pity is it
C. What a pity it isD. How a pity it is
6. As we all know it’s very important forto keep health.
A. weB. ourC. usD. ours
Keys: D A D C C C
