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 theviolin?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：表示计划、安排将要发生的事。Who are we to meet?我们要见谁呀?Im to have supper with John this afternoon.今天下午我要与约翰一起吃晚饭。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 p
