动词
动词是表达句意的精髓，句子的时态、语态等全依靠动词来体现。
动词可分为实意动词（如：go, do, make）、系动词（如：be, remain, seem）、助动词和情态动词（见第七章）
实意动词又可分为及物动词，即可接宾语的词，如：yield, resist, discover；和不及物动词，即不能直接接宾语的词，如：go, begin, happen。有很多词既是及物动词又是不及物动词，如：drop, grow, fail
第一节 不定式
不定式是动词的非谓语形式，它的构成为：to+动词原形，to可视为不定式的标志词，两个动词常用to连接构成不定式。
不定式可以有多种形式，如：主动式（to drink, to see）、被动式（to be continued, to be understood）、完成式（to have completed, to have been adopted）、进行式（to be leaving）等
不定式在句中常作下列成分：
考点一 不定式作宾语、主语或表语
1. 作宾语：不定式多接在谓语动词后作宾语
如：He decided to put in a good word for me at the meeting.
I didn’t expect to hear from you so soon.
常用的可接不定式宾语的动词有：decide, expect, determine, offer, forget, remember, want, prefer, wish, hope, continue, begin, attempt, agree, etc.
例：Human beings are social animals who usually prefer not to live in physical or psychological isolation.
2. 作主语：不定式短语可作主语
如：To see is to believe (百闻不如一见)
To work hard should be your major concern.
注意：由于英文不习惯句子主语过长，不定式主语常被形式主语it所代替(详见第十七章)
例如上面第二句可以变为： It should be your major concern to work hard.
又如： It is very nice of you to help me.
It is hard for you to carry this heavy box.
3. 作表语：当句子的主语是purpose, aim, duty, goal, hope, plan, suggestion, idea, intention, problem, mistake, reaction等表示“意图”、“目的”、“功能”等意思的词时，一般由不定式作表语
如：His only purpose in life is to seek truth.
Our plan was to raise money for the new project.
例题：
(1)
Before the invention of the clock, people had to reliable on the celestial bodies to tell time.
应改为：rely.
解释：此处to是构成不定式的标志词, 之后应接动词原形
(2)
Chinese immigrants began ---- to the United States in large numbers in the middle of the nineteenth century.
(A) come
(B) to come
(C) to have come
(D) have come
答案：B
解释：空格处需要began的宾语，可以是动名词或不定式，A, D是动词原形，可先排除；C是不定式的完成式，不符合begin的用法；只有B正确
(3)
The central purpose of management is for making every action or decision help achieve a carefully chosen goal.
应改为：to make
解释：主语purpose决定应用不定式作表语，故改为to make