'be'的一般现在时
动词'be'在英语中是一个特殊的动词。与其他动词不同，它在一般现在时中形式完全改变。它有三种形式：am、is和are。
掌握了'be'之后，您就可以开始学习一般现在时中的其他动词了。
如何构成'be'的一般现在时？
肯定句
动词'be'在一般现在时中有三种形式：am、is、are。使用哪种形式取决于主语。
| 主语 | 完整形式 | 缩写形式 |
|---|---|---|
| I | I am | I'm |
| you | you are | you're |
| he / she / it | he is / she is / it is | he's / she's / it's |
| we | we are | we're |
| they | they are | they're |
例句：
- I am a teacher.
- She is from Germany.
- They are happy.
- We're students.
- It's cold today.
否定句
构成否定句时，在动词后加'not'。大多数主语有两种缩写形式。
| 主语 | 完整形式 | 缩写形式 |
|---|---|---|
| I | I am not | I'm not |
| you | you are not | you aren't / you're not |
| he / she / it | he is not / she is not / it is not | he isn't / she isn't / it isn't |
| we | we are not | we aren't / we're not |
| they | they are not | they aren't / they're not |
例句：
- I'm not tired.
- He isn't at home.
- They aren't ready.
- We're not late.
- It isn't expensive.
疑问句
构成疑问句时，将am / is / are放在主语前面。
| am/is/are | 主语 | 句子其余部分 |
|---|---|---|
| Am | I | late? |
| Are | you | ready? |
| Is | he / she / it | here? |
| Are | we | on time? |
| Are | they | students? |
例句：
- Are you OK?
- Is she from Spain?
- Are they at school?
- Am I right?
- Is it difficult?
简短回答
简短回答中，我们使用'Yes, [主语] + am/is/are'或'No, [主语] + am not/isn't/aren't'。在肯定的简短回答中不使用缩写形式。
- Are you ready? – Yes, I am. / No, I'm not.
- Is he here? – Yes, he is. / No, he isn't.
- Are they students? – Yes, they are. / No, they aren't.
Wh-疑问句
在句首加上疑问词（who、what、where、when、why、how）。
| 疑问词 | am/is/are | 主语 | 其余 |
|---|---|---|---|
| Where | are | you | from? |
| What | is | your name | ? |
| Who | is | that | ? |
| Why | are | they | late? |
| How | is | she | ? |
例句：
- Where are you from?
- What is your name?
- Who is that man?
- Why are they angry?
- How old is your brother?
什么时候在一般现在时中使用'be'？
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