在英语中什么时候要用be动词（is,am,are）啊?最好用例句来说明!

在英语中什么时候要用be动词（is,am,are）啊?最好用例句来说明!
在英语中什么时候要用be动词（is,am,are）啊?
最好用例句来说明!

在英语中什么时候要用be动词（is,am,are）啊?最好用例句来说明!
现在时 I am,you are,he is,we are,you are,they are （缩略式 I'm,you're,he's,we're,you're,they're）,（否定缩略式 I'm not,isn't,aren't）,过去时 I was,you were,he was,we were,you were,they were （过去时否定缩略式 wasn't,weren't）,过去分词 been,现在分词 being 英语的“be”是个特别动词；有些语言,“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.

表示“……是……”的时候要用到。 例如，I am a student。