助動詞be(am, is, are, was, were, being, been)的用法

(1) be后跟現在分詞構成進行時態。

Who is playing the violin?誰在拉小提琴?

She was reading a book then.那時她正在讀書。

(2)be后跟過去分詞構成被動語態。

He was asked to do the work.有人要他干這件工作。

You are invited to attend the meetintg.有人邀請你參加會議。

(3)be 后跟不定式作謂語，有如下幾種情況：

①表示計劃、安排將要發生的事。

Who are we to meet?我們要見誰呀?

I'm to have supper with John this afternoon.今天下午我要與約翰一起吃晚飯。

②表示指示、命令，否定式表禁止。

You are to see the headmaster today.今天你必須去見校長。

You are not to enter the room without permission.未經允許你不能進入房間。

③表示義務、責任等，同should。You are to be back before 5.你得在5點鐘以前回來。

What is to be done?該干什么。

④表示可能性，與情態動詞may, can同義。

Such books are to be found in any library.這種書任何圖書館都有。

Not a sound was to be heard.一點聲響也沒有。

⑤表示后來發生的事，可以用來表示命運或注定

They say good-bye, little knowing that they were never to meet again.他們告別了，沒想到再也不能相見了。He was to regret the decision.他有一天會后悔做出這一決定的。

⑥用于習語

Where am I to go? 我該向何處去?

What am I to do? 我該怎么辦?

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