助动词be(am, is, are, was, were, being, been)的用法

助动词一般没有词意，不能单独作谓语动词。其作用在于帮助构成各种时态、语态、否定、疑问等。

  1、助动词be(am, is, are, was, were, being, been)的用法

  (1) be后跟现在分词构成进行时态。

  Who is playing the violin?谁在拉小提琴?

  She was reading a book then.那时她正在读书。

  (2)be后跟过去分词构成被动语态。

  He was asked to do the work.有人要他干这件工作。

  You are invited to attend the meetintg.有人邀请你参加会议。

  (3)be 后跟不定式作谓语，有如下几种情况：

  ①表示计划、安排将要发生的事。

  Who are we to meet?我们要见谁呀?

  I'm to have supper with John this afternoon.今天下午我要与约翰一起吃晚饭。

  ②表示指示、命令，否定式表禁止。

  You are to see the headmaster today.今天你必须去见校长。

  You are not to enter the room without permission.未经允许你不能进入房间。

  ③表示义务、责任等，同should。

  You are to be back before 5.你得在5点钟以前回来。

  What is to be done?该干什么。

  ④表示可能性，与情态动词may, can同义。

  Such books are to be found in any library.这种书任何图书馆都有。

  Not a sound was to be heard.一点声响也没有。

  ⑤表示后来发生的事，可以用来表示命运或注定

  They say good-bye, little knowing that they were never to meet again.他们告别了，没想到再也不能相见了。

  He was to regret the decision.他有一天会后悔做出这一决定的。

  ⑥用于习语

  Where am I to go? 我该向何处去?

  What am I to do? 我该怎么办?