(1) 从上两例中看出，do / does / did 代替动词。

　　He translated the article better than I did. （did代替wrote it）

　　— Do you think she is clever?

　　— I think so. （so代替 she is clever）

　　(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。

　　— 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.

　　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。

　　— 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。）

　　(5) 为使语言精炼，避免不必要的重复，对话中常用省略形式。

　　— 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.）