英语中，为了避免不必要的重复，经常用so, not, to, do, does 代替前面出现的动词或相关内容。
如：He translated the article better than I did. (did代替wrote it)
— Doyou think she isclever?
— I think so. (so代替 she is clever)
(1) 从上两例中看出，do / does / did 代替动词。
(2) "so 与 not" 代替某个词、短语、句子等，通常用于hope, think, believe, expect, suppose, be afraid, fear, imagine, etc后作宾语。
E.g. — Is it correct?
— I'm afraid not. (not correct)
(3) "to" 用作不定式，常跟随下列动词：want, mean, hope, expect, refuse, seem, intend, be, afraid, etc.
E.g. I asked him to go to the party, but he refused to. (go to the party)
(4) "do so, do that, do it" 用来代替动态动词，而不能代静态动词。
Eg. — He gave up studying English.
— Why did he do so? (= give up studying English)
— The dish tastes nice.
— Yes, so it does. (tastes nice)
(此句不能用it does it 或 it does so, 因taste属静态动词。）
E.g. — He is thinking of buying a car?
— Is he?（这里，“thinking of buying a car”被省略了。）
— Will he come back in time?
— Perhaps.（省略了he will come back in time.)
1. — Shall I wake you up tomorrow? — Yes, ________ .
A. please do B. you shall
C. you will D. you may
2. I think records are often ________ an actual performance.
A. as good as or better than B. as good or better than
C. like good or better than D. as good as any other
3. — If he doesn't come to work, he may be fired. — Surely he isn't so foolish ________ not to realize that.
A. so B. and C. but D. as
4. — Don't you think Alan's health has beenruined by smoking? — Yes, he told me ________ himself.
A. the fact B. this thing C. It D. so
5. — Will you go home tomorrowevening? — No, I'm going to a lecture, or at least, I'm planning ________ .
A. on B. to C. so D. It
6. — I slipped on the stairs, I think my arm is broken. — Oh! I ________ .
A. do not hope so B. do not hope C. hope not so D. hope not
A. Florida also B.
C. Florida is as well D. so does
8. — Have you been here long? — ________ .
A. No, not very B. Not much
C. Yes, only little D. No, only yesterday
9. — You look happy today, Mary. — I like my new dress and mother ________, too.
A. does B. likes C. is D. do
10. — So you are lost, little boy. Why didn't you hang on to your mother's skirt?
— ________, but I couldn't reach it.
A. I hanged to B. I did to
C. I didn't hang to D. I tried to