If引导的条件状语从句与Iff引导的虚拟句有什么区别

If引导的条件状语从句与Iff引导的虚拟句有什么区别
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青蛙王子LOVEYOU 1年前 已收到1个回答 举报

jiejie779898 幼苗

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条件状语从句
连接词主要有 if, unless, as/so long as, on condition that 等.if 引导的条件句有真实条件句和非真实条件句两种.非真实条件句已在虚拟语气中阐述.
unless = if not.  例如:
Let's go out for a walk unless you are too tired. 如果不太累,我们去散散步.
If you are not too tied, let's go out for a walk.
You will be late ___ you leave immediately. 
A. unless  B. until  C. if  D. or
答案A.句意:除非你立即走,否则你就回迟到的.可转化为 If you dong leave immediately, you will be late.B、D句意不对,or表转折,句子如为 You leave immediately or you will be late.
虚拟语气
1)虚拟语气用来表示说话人的主观愿望或假想,所说的是一个条件,不一定是事实,或与事实相反.虚拟语气在条件句中应用比较多.
2)条件句可分为两类,一类为真实条件句,一类为非真实条件句.非真实条件句表示的是假设的或实际可能性不大的情况,故采用虚拟语气.
真实条件句用于陈述语气,假设的情况有可能发生.
一般现在时
shall/will + 动词原形
祈使句 情态动词一般现在时
例如:If he comes, he will bring his violin. 如果他来,会带小提琴来的.
The volleyball match will be put off if it ___. 
A. will rain  B. rains  C. rained  D. is rained
答案B.真实条件句主句为将来时,从句用一般现在时.
注意:
1)在真实条件句中,主句不能用be going to表示将来,该用shall, will.
(错) If you leave now, you are never going to regret it.
(对) If you leave now, you will never regret it.
2)表示真理时,主句谓语动词不用shall (will) +动词原形,而直接用一般现在时的动词形式.
非真实条件句
1)虚拟语气可以表示过去,现在和将来的情况,时态的基本特点是时态往后推移.
a. 与现在事实相反的假设
一般过去时(be用were)should(would)等 +动词原形
例如:If they were here, they would help you. 如果他们在这儿,会帮助你的.
含义:They are not here, they can’t help you.
b. 与过去事实相反的假设
过去完成时
should(would)等+ have+ 过去分词
例如:If he had come yesterday, I should / would have told him about it.如果他昨天来的话,我会把这件事告诉他的.
含义:He did not come yesterday, so I did not tell him about it.
c. 表示对将来不大可能发生的事情的假想
一般过去时
should/would等 + 动词原形
were+ 不定式
should+ 动词原形
例如:If you succeeded, everything would be all right. 如果你将来成功了,一切都会好的.
If you should succeed, everything would be all right.
If you were to succeed, everything would be all right.
含义:You are not likely to succeed, everything will be what it is now.

1年前

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