初中英语知识点：Be动词定义及用法(3)

　　3、be 动词用在特殊疑问句

　　在特殊疑问句里，be 动词仍然移到主语前面，但特殊疑问句是以特殊疑问词开头的，所以be 动词只能说是移到主语前面，或者说是在特殊疑问词的后面。例如：

　　Whose bike is broken? Xiao Ming's bike is.

　　Who was singing in the room? Mr. Zhang was.

　　Where are you from? I am from Wuhu.

　　What class were you in? We were in Class 2.

　　How old is Tom? He is ten.

　　4、be 动词的否定句

　　be 动词做谓语时，它的否定形式是在be 后加not，并且可以缩写。例如：

　　It is not sunny today.

　　Tom and his friends are not in the park.

　　You were not nine years old when I went to the university.

　　He was not often late for his class when he was a student.

　　I wasn't here yesterday.

　　My parents weren't at home last Sunday.

　　5、be 动词的祈使句

　　be 动词的祈使句有肯定和否定两种形式。肯定形式是以be 动词开头，而否定形式或强调句形，要加don't 或do。例如：

　　Be careful!

　　Be a good boy!

　　Don't be silly!

　　Don't be a fool!

　　Do be obedient!

　　Do be careful.

　　二、be 动词做助动词

　　助动词be 有两个基本用法，一是与谓语动词一起构成各种时态，二是构成被动语态。

　　1、“be + 现在分词组”成各种进行式时态。例如：

　　Tony's maid is washing his new car.

　　The children are playing in the field.

　　Samuel was eating when I came in.

　　We have been living here since 1959.

　　This time next day they will be sitting in the cinema.
 

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