不定式的特殊句型so as to

　　1) 表示目的;它的否定式是so as not to do。

　　Tom kept quiet about the accident so as not to lose his job.　湯姆對事故保持沉默是為了不丟掉他的工作。

　　Go in quietly so as not to wake the baby. 輕點進去，別驚醒了嬰兒。

　　2) so kind as to ---勞駕

　　Would you be so kind as to tell me the time? 勞駕，現在幾點了。

　　不定式的特殊句型Why not

　　"Why not +動詞原形"表達向某人提出建議，翻譯為："為什么不……?" "干嗎不……?"

　　例如：Why not take a holiday?　干嗎不去度假?

　　不定式的時態和語態

　　1) 現在時：一般現在時表示的動詞，有時與謂語動詞表示的動作同時發生，有時發生在謂語動詞的動作之后。

　　He seems to know this.

　　I hope to see you again. = I hope that I'll see you again.　我希望再見到你。

　　2) 完成時：表示的動作發生在謂語動詞表示的動作之前。

　　I'm sorry to have given you so much trouble.

　　He seems to have caught a cold.

　　3) 進行時： 表示動作正在進行，與謂語動詞表示的動作同時發生。

　　He seems to be eating something.

　　4) 完成進行時：

　　She is known to have been wreaking on the problem for many years.