20.一般现在时（the present indefinite tense）
英语动词有多种不同形态表示不同的时间关系，称为时态。最常用的时态之一是一般现在时，主要表示:
1.现在的或一般的情况或状态：
i'm sorry i'm late.
对不起我迟到了。
you speak good english．
你英文讲得很好。
he is very tired．
他现在很疲倦。
2.经常或习惯性的动作：
we often write to each other．
我们时常通信。
she works very hard.
她很用功。
they go jogging every day．
他们每天跑步。
3.表示将要发生的情憾(仅限于少数动词)：
what time do we arrive in shanghai?
我们什么时候到达上海?
the train leaves at 2:30 pm．
火车下午两点半开。
这时态的肯定、否定、疑问及简短回答形式如下：
1.肯定句:
i (you, they) like sports.
he (she) likes sports.
2.否定句:
i (you, they) don't like sports.
he (she) doesn't like sports.
3.疑问句:
do you (we, they) like sports?
does he (she) like sports?
4.简短回答:
i (we, they) do.
i (we, they) don't.
yes, he (she) does.
no, he (she) doesn't.
动词be的四种形式：
1.肯定句：
i am a student.
you are a student.
he (she) is a student.
we (you, they) are students.
2.否定句:
i am not a student.
you are not a student.
he (she) is not a student.
we (you, they) are not students.
3.疑问句:
am i a student?
are you a student?
is he (she) a student?
are we (you, they) students?
4.简短回答:
yes, i am.
yes, you are.
yes, he (she) is.
no, i'm not.
no, he (she) isn't.
no, we (you, they) aren't.