由if和unless引导的条件状语从句

1. If we lose our short-term memory, we forget things happening recently.

译：

2. If the picture is silly, strange and colorful, you will remember it better. 译：

A: If sentences: actions with definite results.有必然结果发生的行动eg:① If you go into a clothes shop, you find clothes.

②If you go into a car showroom, you see cars.

③Water turns into ice if you cool it.

④The wood floats if you put it into water.

Conclusion:

1) . 如果if 条件句谈论的是重复发生和预示必定要发生的情景和事件，则主从句大多用一般现在时态。

2) . 在if 条件句中，if 条件从句可以放在前面，也可以放在后面。当if 引导的条件从句放在前面时，后面常用逗号隔开。

B: If sentences: actions with possible results 有可能性结果发生的行动eg: If you ask him，he will help you．如果你请他帮忙，他会帮你的。

If you fail in the exam，you will let him down．

在if 引导的条件状语从句中,如果从句谈论的是一个有可能发生的事实及其产生的相关的结果，主句用一般将来时态，从句用一般现在时态。

C: unless引导的条件状语从句：unless= if ......... not. con除非，若不，除非•••(否

则)

e.g.: Let's go out for a walk unless you are too tired.

= If you are not too tied, let's go out for a walk. 我们出去散步吧，除非是你太累。译：如果你不早点出发,你就不能及时赶到那儿。

我们可以把unless或if…not从句放在句子开头或末尾。

You will be late for school unless you leave now. = Unless you leave now, you will be late for school. 除非你早点出发，（否则）你上学会迟到。

You will be late for school if you don 't leave now. =

If you don ' t leave now, you will be late for schoo如果你不早点出发，你上学迟

1. If we lose our short-term memory, we forget things happening recently.译：

到。

“if引导的条件状语从句的用法，现在总结一下：

1) 引导条件状语从句最常用的连词是if o if引导的条件句有真实条件句和非真实条件句两种(非真实条件句会在以后的虚拟语气中阐述)，其引导的真实条件状语从句表示在某种条件下某事很可能发生。

2) if条件句不一般，几个要点记心间；条件句，放在前，逗号要放句中间。

条件句表可能，主句多用将来时；条件句表事实，主句常用现在时。

【巩固练习】

一.if和uni ess句型互改。

Eg: You will fail the exam if you don ' t work hard.

=You will fail the exam uni ess you work hard.

1) Uni ess you obey the rules, you will be puni shed.

2) A fish dies if you don ' t keep it in the water.

3) No body can learn English well if he doesn ' t work hard on it.

4) Un less you start right now, you will be late for the meet ing.

二.用if 或uni ess 填空。

1. ________ you put wood into water, it floats.

2. I sleep with the window open ________ it is really cold.

3. You will not improve your skill in a short time __ you practice playi ng the violin regularly.

4. Ice melts __________ you heat it.

5. ______ you boil water, it becomes steam (蒸汽).

6. ______ you don ' t work hard, you will fail the exam.

7. He can ' t be here on time _____ he gets up early.

8. ______ you don ' t have eno ugh sleep, you will feel tired.

9. ______ it is fine tomorrow, I will go fishing with my dad.

10. _____ you finish your homework, you will not go out to play.

三.单项选择。

1. You will not remember the facts ______ you understand them well.

A. if

B. uni ess

C. if not

D. because

2. Shenzhen ______ a dirty place if we ______ the ground.

A. is; litter

B. will be; will litter

C. is; are litteri ng

D. will be; litter

3. If you ______ harder, you will fail the exam.

A. not work

B. work

C. don ' t work

D. won ' t work

4. _____ you obey the rules, you will be punished.

A. If

B. Since

C. Because

D. Uni ess

5. He can ' t see the words on the board uni ess he his glasses.