时态(1)
一、一般现在时的用法
1) 经常性或习惯性的动作，常与表示频度的时间状语连用。
时间状语：every…, sometimes, at…, on Sunday
I leave home for school at 7 every morning.
He cycles to work every day.
2) 客观真理，客观存在，科学事实。
The earth moves around the sun.
Shanghai lies in the east of China.
Water boils at 100 centigrade degrees.
3) 表示格言或警句中。
Pride goes before a fall. 骄者必败。
注意：此用法如果出现在宾语从句中，即使主句是过去时，从句谓语也要用一般现在时。例如：
Columbus proved that the earth is round.
4) 现在时刻的状态、能力、性格、个性。
I don't want so much.
Ann Wang writes good English but does not speak well.
比较：Now I put the sugar in the cup.
I am doing my homework now.
第一句用一般现在时，用于操作演示或指导说明的示范性动作，表示言行的瞬间动作。再如：Now watch me, I switch on the current and stand back. 第二句中的now是进行时的标志，表示正在进行的动作的客观状况。
知识扩展：一般现在时表将来
1)下列动词：come, go, arrive, leave, start, begin, return的一般现在时表将来。这主要用来表示在时间上已确定或安排好的事情。
The train leaves at six tomorrow morning.
When does the bus star? It stars in ten minutes.
2)倒装句，表示动作正在进行，如：
Here comes the bus. = The bus is coming.
There goes the bell. = The bell is ringing.
3)在时间或条件句中。
When Bill comes (不是will come), ask him to wait for me.
I'll write to you as soon as I arrive there.
4)在动词hope, take care that, make sure that等后。
I hope they have a nice time next week.
Make sure that the windows are closed before you leave the room.
二、一般过去时的用法
1)在确定的过去时间里所发生的动作或存在的状态。
时间状语有：yesterday, last week, an hour ago, the other day, in 1982等。
Where did you go just now?
I saw Tom in the street yesterday.
I bought this TV set in Beijing last year.
2)表示在过去一段时间内，经常性或习惯性的动作。
When I was a child, I often played football in the street.
He always went to work by bus.
3)用过去时表示现在，表示语气委婉礼貌。
(1)动词want, hope, wonder, think, intend 等。例如：
Did you want anything else?
I wanted to ask you about that.
Did you want to speak to me now?
I wondered if you could help me.
(2)情态动词 could, would，例如：
Could you lend me your bike?
4)用在条件句中表示与现在或将来事实不符的虚拟语气。
If I were a bird, I would fly to Beijing.
If he were here now, we could turn to him for help.
He used to act like that.
注意比较下列句型：
◎ It is time for sb. to do sth “到……时间了;该……了”，例如：
It is time for you to go to bed. 你该睡觉了。
◎ It is time sb. did sth. “时间已迟了;早该……了”，例如：
It is time you went to bed. 你早该睡觉了。
◎ would (had) rather sb. did sth. 表示“宁愿某人做某事”，例如：
I'd rather you came tomorrow.
一般过去时表示的动作或状态都已成为过去，现已不复存在。
Christine was an invalid all her life. (含义：她已不在人间。)
Christine has been an invalid all her life. (含义：她现在还活着。)
Mrs. Darby lived in Kentucky for seven years. (含义：达比太太已不再住在肯塔基州。)
Mrs. Darby has lived in Kentucky for seven years. ( 含义：现在还住在肯塔基州，有可能指刚离去。)
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