电子商务的历史:在句子里be的作用给我详细的教我吧 详细 谢谢 0 离问题结束还有 14 天

英语的“be”是个特别动词；有些语言，如中文和马来文，并没有“be”这样的动词。
“Be”除了原形的“be”之外，还有另外七种形式：am, is, are, been, being, was, were.
在句子中，“be”可以是主动词(The Principal Verb)或助动词(The Auxiliary Verb).
当主动词时，“be”在性质上属于接系动词(The Linking Verb), 后面要有名词、形容词、地方副词或短语作补足语(The Complement)。例如：
1. The man is a science teacher.
2. Mary\'s new dresses are colourful.
3. I have been there before.
4. Mother is in the kitchen now.
这四个都是陈述句，可以变成疑问句，方法简单，把主语和“be”或助动词对换位置即可：
5. Is the man a science teacher?
6. Are Mary\'s new dresses colourful?
7. Have I been there before?
8. Is mother in the kitchen now?
当“be”要在祈使句中出现时，它必须借重助动词“do”或“don\'t”之助，如：
9. Don\'t be silly!
10. Do be obedient!
11. Don\'t be a fool!
“Be”有两种缩写法，如下：
12. He\'s not...../He isn\'t....
13. You\'re not...../You aren\'t...
但“am + not”的缩写法只有一个：
14. I\'m not.
有人用“ain\'t”, 但这并不是标准英语。
谈过了“be”作主动词的功能，现在看看“be”作助动词时，有些什么用法：
1.“Be + 现在分词”以组成进行式时态(Continuous Tenses)，如：
15. Tony\'s maid is washing his new car.
16. The children are playing in the field.
17. Samuel was eating when I came in.
18. We have been living here since 1959.
2.“Be + 过去分词”以组成被动语态(The Passive Voice),如：
19. Her money in the drawer was stolen.
20. A number of good jobs are taken up byforeigners.
21. David studied in Taiwan but has been trained as a language lecturer in America.
22. Can all the wonderful birds be found in our Bird Park?
23. The disobedient boy was told to stand out- side the classroom.
24. Steps are being taken to reduce traffic con- gestion during peak hours.
25. Dishonest students will be immediately dealt with.
从上面例子看，“be”这动词外貌平凡，但内涵丰厚。如果没有“be”，补足语的桥梁断了。如果没有“be”,何来进行式时态和被动语态？缺了这几样重要的句式，英语还像英语吗？

be是一个连系动词,意思不完整,不能独立做谓语,只能加上表语构成"系表"结构.如:I am a student.
be,的原意为,"是,是的"常用于回答,例如"yes,I am."
还可以用来作为一般疑问句的提问:Is his your father?
be ,还可以用作助词,也就是说它没有任何意思,起着构成句子完整性.
如被动语态,被动语态的结构"be+动词的过去分词"
例如This desk is made of mood.
be 常用其过去式were用于虚拟语气中,注意一定要用were,不能用was,
例如;If I were a bird,i would fly to the USA.如果我是一只鸟,我要飞去美国.