一、常用一般现在时的情况：
1.以Here或There开头的句子，说明正在发生的动作，谓语动词不用现在进行时，而用一般现在时。如：
Here comes the bus!
There goes the bell!
2.既定的时间如生日、日历、课时安排、交通时刻表等，通常用一般现在时表示将来动作。如：The meeting starts at five o'clock.
The train leaves at three this afternoon.
3.在see to it，make sure，make certain，be sure，look out，take care等之后的从句要用一般现在（过去、现在完成）时代替一般将来（过去将来、将来完成）时。如：
You must make sure the door is closed before you leave the lab.
See to it that everything is OK.
4.在宾语从句中，表示客观事实或真理，一律用一般现在时。如：
The teacher taught us yesterday that the moon circles the earth.
Somebody told me that you are a writer.
5.在由as soon as，when，before，after，till等引导的时间状语从句和由if，unless，as long as，in case等引导的条件状语从句或在方式、让步状语从句中，常用一般现在时代替将来时，但主句用一般将来时。如：
If you come this afternoon，We'll have a meeting.
When you meet him，tell him to come to my place.
二、常用一般过去时的情况：
1.表示说话人始料未及的事情，用一般过去时。如：
Oh! I didn't know you were in Shanghai. How long have you been there?
2.在wish，would rather的宾语从句中和在as if引导的状语从句中，以及在It is time that…的定语从句中，谓语动词用一般过去时说明现在的事情。如：
It's time you had a holiday.
He looks as if he were young.
3.用表示意愿及精神状态的动词，反映的是说话者探询的态度时，动词用一般过去时表示一般现在时，显得更加有礼貌。如：
I didn't know you were here.（我不知道你在这里，were实际上指现在）
I wondered if you could help me.
4.在含有hardly/scarcely…when，no sooner…than结构的句子中，主句用过去完成时，从句用一般过去时。（注意：主句一般倒装）如：
Hardly had I entered the room，when I heard a loud noise.
No sooner had he reached the door than he came back.
三、常用现在进行时的情况：
1.若句中带有always，all the time，forever，constantly等词或短语，用进行时表示一个频繁发生的动作，表示说话人赞赏或厌恶等感情。如：
You are always forgtting the important things.
He is constantly leaving his things behind.
2.某些词，如come，go，leave，arrive，start等可用现在进行时表示将来。
He is leaving tomorrow.
The visitors are arriving in a few minutes.
四、常用过去进行时的情况：
1.表示故事发生的背景。如：
One day Jones was walking along the street.
It was snowing as they made their way to the front.
2.与always，forever，constantly，continually，frequently等词连用，表示过去经常发生的行为，往往带有感情色彩。如：
My brother was always losing his key.
They were frequently quarrelling.
五、常用现在完成时的情况：
1.被the first time，a few times，again and again等表示次数或重复的状语修饰时，句中常用现在完成时。如：
This is the third time we have made improvements in that equipment.
2.定语从句的先行词是最高级形式或被最高级形容词修饰时，句中常用现在完成时。如：
Scientists have found almost all metals are good conductors，the best of which is silver.
3.在某些时间状语从句和条件状语从句中，用现在完成时表示将来完成的动作。如：
I'll go to your home when I have finished my homework.
If it has stoppted snowing in the morning，we'll go to the park.
六、常用过去完成时的情况：
1.某些动词的过去完成时表示原先计划或打算做而没做的事情。常见的动词有mean，plan，think，suppose，want，intend等。如：
We had hoped that you would be able to visit us.
I had intended to make a cake，but I ran out of time.
2.在条件状语从句中以及which或I'd rather后的宾语从句中，常用过去完成时表示与过去事实相反的虚拟语气。如：
If you only had worked with great care!
I would rather you had told her the truth.
七、常用一般将来时的情况：
1.表示一种倾向、固有特性或说话人推测的意见。如：
I think it will rain tomorrow.
Birds will build nests.
2.在某些条件状语从句、时间状语从句中。如：
We shall go unless it rains.
He'll help you if you ask him.
说明：有时用be about to+动词原形或be to +动词原形或be going to +动词原形表示将来时。如：
The meeting is going to start at nine.
Tell her she is not to be back late.
The film is about to begin.
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