八年级英语语法主将从现知识点精讲及专项练习

八年级英语语法主将从现知识点精讲及专项练习

主将从现定义：

主将从现是指在时间状语从句和条件状语从句中，如果主句是一般将来时，从句用一般现在时替代一般将来时。引导时间状语的引导词

when , while , before , after , untill , till , since , as soon as

主将从现一般出现的四种情况：

一、如果主句是将来时或表示将来含义时，那么条件和时间状语从句多用一般现在时

如：When I grow up, I will be a nurse and look after patients/ I want to be a nurse and look after patients.

我长大后要当一名护士，照顾病人。

二、如果主句是祈使句，那么从句通常要用一般现在时

如：Don’t laugh at me when I make a mistake.

我犯错误的时候不要笑话我。

三、如果主句是含有情态动词的一般现在时，根据需要从句多用一般现在时

如：You should be quiet when you are in the reading room

在阅览室时应保持安静。

when引导的时间状语从句

例句展示：

As soon as I reach Canada, I will ring you up. 我一到加拿大，就给你来电话。

I’ll call you as soon as I get home.我一到家就给你打电话。

I’ll wait here until/till the rain stops.我将在这里等着，直到雨停。

You can’t go home until/till you finish your work.直到你完成你的工作，你才能回家。

I will tell you after they leave. 等他们走后我再告诉你。

We must strike while the iron is hot. 我们必须趁热打铁。

Be careful when you cross the road.过马路时要小心。

You can feel the air moving as your hand pushes through it.当你的手在空气中挥动的时候，你就能感觉到空气在流动。

You can sit here before you leave.在你离开之前，你可以坐这儿.

After you think it over, please let me know what you decide.你仔细考虑过以后，告诉我你是怎样决定的。

Please wait until I arrived.在我到达之前请等我。

As soon as I reach Canada, I will ring you up. 我一到加拿大，就给你来电话。

I’ll come to see you before I leave.在我离开之前我会来看你。

I’ll go out for a walk after I finish my work.我完成工作之后，我会出去散步。

I have lived in Shanghai since I left Hubei.

if引导的条件状语从句

1．if从句用一般现在时，主句用一般将来时

If he runs he’ll get there in time. 如果他用跑的，他就会及时赶到那儿。

The cat will scratch you if you pull her tail. 如果你拉猫的尾巴，它就会抓你。

2．if从句用一般现在时，主句用may/might/can

If the fog gets thicker the plane may/might be diverted. 如果雾在大一些，飞机可能就会改在别的机场降落。

If it stops snowing we can go out. 如果雪停了，我们就可以出去。

3．if从句用一般现在时，主句用must/should

If you want to lose weight you must/should eat less bread. 如果你想减肥，你必须少吃面包。

If you do, you’ll be sorry.

if引导的条件状语从句表示假如从句的动作发生，主句的动作就（不）会发生。

[解码句子结构]

if 引导的条件状语从句位置灵活，可直接放在主句后面，也可以放在句首。放在句首时，从句后面要用逗号和主句隔开。如：

I’ll go to see you if I have time. 如果有时间，我就去看你。

If it rains tomorrow, we’ll stay at home. 如果明天下雨，我们就呆在家里。

总结：

在复合句中：⑴当主句是一般现在时或是一般将来时时；（2）当主句是祈使句时；（3）当主句含有情态动词时，if引导的条件状语从句通常用一般现在时。如：

If she doesn’t come, she will be sorry. 如果她不来，她会遗憾的。

Have a good rest if you are tired. 如果累了，你就好好休息一下。

We must study hard if we want to pass the final exam. 如果想通过期末考试，我们必须努力学习。

[同义句转换]

1. 用“祈使句＋and / or ＋一般将来时的句子”转换。如：

If you work hard, you’ll pass the exam easily. → Work hard, and you’ll pass the exam easily. 努力学习，你将很容易通过考试。

If you don’t hurry up, you’ll miss the train. → Hurry up, or you’ll mis s the train. 快点儿，否则你就赶不上火车了。

2. 用含介词with或without的介词短语转换。如：

If there is no water, fish can’t live. → Fish can’t live without water. 离开水，鱼不能生存。

配套练习题：

一、单项选择

1. If you _____ to the party, you’ll have a great time.

a. will go

b. went

c. go

d. going

2. It will be a long time ____ peter _____ his work.

a. since, has finished

b. after, finishes

c. when, will finish

d. before, finishes.

3. What will father _____ us from Japan?

a. take

b. bring

c. carry

d. make

4. Weifang is famous ______ kites

a. for

b. to

c. on

d. with

5.I ____ her the answer if she ____me.

a. can tell, will ask

b. will tell, will ask

c. would tell, ask

d. will tell, asks

6. – What are you going to do tomorrow?

--We’ll go to the library tomorrow if it ___.

a. isn’t rain

b. rain

c. won’t rain

d. doesn’t rain

7.—Do you know when he will come back tomorrow?

--Sorry, I don’t know. when he ____ back, I’ll tell you.

a. comes

b. will come

c. come

d. may come

8. What will you do if you _____ to the old folk’s home visit?

a. go

b. went

c.going

d. will go

9. If I eat ____ food, I’ll be very fat.

a. too many

b. many too

c. too much

d. much too

10. I’ll give the book to him if he ___ here next Sunday.

a. will come

b. comes

c. is coming

d. came 11. There ____an English film in our school tomorrow.

a. is going to have

b. will have

c. is going to be

d. has

12. Could you tell us where ____？

a. will the next Olympic Games held

b. the next Olympic Games will be held

c. would the next Olympic Games be held

d. the next Olympic Games would be held

13. When my mother returned last night, I ____ a book.

a. read

b. am reading

c. was reading

d. am going to read

14. What ____ you ____ when it began to rain?

a. do, do

b. were, doing

c. are, doing

d. did, do

15.I’ll wake you up when he ____back.

a. will

b. is going to come

c. comes

d. come

1---5 cdbad 6---10 daacb 11---15 cbcbc

二、完成句子

1.如果他到的晚了会发生什么事情？

What _will ______________ if he ___ __________ late?

2.如果努力学习，你就会取得好成绩。

If you___ ______ __hard______, you _______ _____ good __________.

3.他如果看电视太久了，他的父母会不高兴。

If he_________ ______ too much, his parents ______ ______unhappy.

4.如果我们为他组织生日聚会，大家都会来的。

Everyone ______ _____ if we ______a birthday party ______ him.

5.如果明天不下雨，我会和你一起去公园的。

If ___doesn’t________tomorrow,I ____ go to the park _____you.

6.如果她睡过头了，就会旅游迟到的。

She_____ _____ late for the trip if she ________.

7.如果他有空，他会帮助你的。

If he ______, he _______you.

8.如果tom考试不及格，他就没有机会上高中了。

Tom _____have the _________to go to the high school if he _______the exams.

9.你如果抄同学的作业就不能学好各门功课。

You _______ ______ good at all the subjects if you _______ the other students’ homework.

10. 如果你参加聚会，你将会过得很开心。