状语从句
状语从句中的主谓省略遵循下面原则： （1）当状语从句的主语与主句的主语一致时且从句中含有BE 动词的某种形式时，可以省略状语从句的主语和系动词be ，这时从句中可出现如下结构：
如：Work hard when (you are) young ,or you'll regret.趁年轻要努力学习，要不然你会后悔 如：He looked everywhere as if (he was)in search of something .他到处看似乎在找什么东西。 如：The exhibition is more interesting than (it was) expected .这次展览比被预料的有趣的多
如：Olympic gold medallist hurdler Liu Xiang opened his lips as if (he were) to speak .
奥林匹克金牌获得者跨栏运动员刘翔张开嘴好象要说什么。
（2）当从句的主语与主句的主语不一致，但从句主语是 it ，从句中又含有系动词be 的某种形式时 ，可以把it 和系动词be 一起省略。
Unless (it is) necessary ,you'd better not refer to the dictionary.如果没有必要，你最好不要查字典。 Whenever (it is )possible, you should come and help. 不管什么时候只要有可能就来帮忙。 Y ou should let us know the result as soon as(it is) possible. 你应尽快让我们知道结果。 Send the goods now if (they are) ready. 货物如果准备好了，请送过来。
虚拟语气
If (it is) necessary, ring me at home. 如果有可能，朝我家里打电话。 Come along with me if (it is) possible. 如果有可能和我一起去吧. 。
If (it is) true, this will casue us a lot of trouble. 如果是真的，这会给我们带来很多麻烦。 There are few people nowadays, if (there are) any, who remember him. 很少有人能记起他。
当条件状语从句表示的行为和主句表示的行为所发生的时间不一致时, 动词的形式要根据它所表示的时间来调整。例如:
If I were you, I would have gone home.
If you had followed the doctor's advice,you would be quite all right now.(从句说的是过去, 主句指的是现在。) If the weather had been more favorable ,the crops would be growing still better.
虚拟语气用于表语从句、同位语从句
n. 要求：demand requirement request motion pray insistence 建议：suggestion advice proposal recommendation motion 命令、决定：order command decision determination resolution
其它：plan desire idea necessity preference等名词的表语从句和同位语从句, 其谓语动词要用虚拟语气的结构"(should)+动词原形" 。例如:
We all agreed to his suggestion that we(should)go to Beijing for sightseeing. My idea is that he (should)do exercises first. 3. 含蓄条件句
在某些虚拟语气结构中没有if 条件句, 虚拟条件是用其它形式表示出来, 这种现象在语法上称为" 含蓄条件" 。含蓄条件具体分为以下几种情况:
1) 通过动词不定式短语表示条件。例如: Y ou would be a fool to refuse his offer.
(=If you should refuse his offer,you would be a fool.) 要是你拒绝他的建议, 就太傻了。
2) 通过介词短语表达条件。
要不是那场暴雨, 我早就到达了。
3) 通过连词: She came to town yesterday,otherwise/or I would not have met her. 昨天她到城里来了, 不然我就不会遇见她了。
(otherwise/or=if she hadn't come)
I would have attended the meeting,but I have been too busy.(=...if I had not been too busy) 我本来要参加会议的, 只是太忙了。
4) 通过Were it not for...或Had it not been for...等句式表达条件。意为" 如果当时没有……",表示同过去事实相反的假设。例如:
Were it not for(=If it were not for) the leadership of the Party,we could not live a happy life. 要不是党的领导, 我们不可能过幸福生活。 (与现在事实相反)
Had it not been for(=If it had not been for) the leadership of the Party,we should have failed. 若不是有党的领导, 我们早就失败了。 (与过去事实相反)
5) 通过分词短语表达条件。例如:
Given more attention,the trees could have grown better.倘若给予更多的关心, 这些树本来可以生长得更好的。 (=If they had been given more attention...) :
Such mistakes could have been avoided.这种错误本来可以避免的。
(暗含条件从句if we had been more careful)
It was so quiet,you could have heard a pin drop.是那样的安静, 掉根针你都听得见。 (暗含条件从句if it had dropped to the ground)
状语从句
状语从句中的主谓省略遵循下面原则： （1）当状语从句的主语与主句的主语一致时且从句中含有BE 动词的某种形式时，可以省略状语从句的主语和系动词be ，这时从句中可出现如下结构：
如：Work hard when (you are) young ,or you'll regret.趁年轻要努力学习，要不然你会后悔 如：He looked everywhere as if (he was)in search of something .他到处看似乎在找什么东西。 如：The exhibition is more interesting than (it was) expected .这次展览比被预料的有趣的多
如：Olympic gold medallist hurdler Liu Xiang opened his lips as if (he were) to speak .
奥林匹克金牌获得者跨栏运动员刘翔张开嘴好象要说什么。
（2）当从句的主语与主句的主语不一致，但从句主语是 it ，从句中又含有系动词be 的某种形式时 ，可以把it 和系动词be 一起省略。
Unless (it is) necessary ,you'd better not refer to the dictionary.如果没有必要，你最好不要查字典。 Whenever (it is )possible, you should come and help. 不管什么时候只要有可能就来帮忙。 Y ou should let us know the result as soon as(it is) possible. 你应尽快让我们知道结果。 Send the goods now if (they are) ready. 货物如果准备好了，请送过来。
虚拟语气
If (it is) necessary, ring me at home. 如果有可能，朝我家里打电话。 Come along with me if (it is) possible. 如果有可能和我一起去吧. 。
If (it is) true, this will casue us a lot of trouble. 如果是真的，这会给我们带来很多麻烦。 There are few people nowadays, if (there are) any, who remember him. 很少有人能记起他。
当条件状语从句表示的行为和主句表示的行为所发生的时间不一致时, 动词的形式要根据它所表示的时间来调整。例如:
If I were you, I would have gone home.
If you had followed the doctor's advice,you would be quite all right now.(从句说的是过去, 主句指的是现在。) If the weather had been more favorable ,the crops would be growing still better.
虚拟语气用于表语从句、同位语从句
n. 要求：demand requirement request motion pray insistence 建议：suggestion advice proposal recommendation motion 命令、决定：order command decision determination resolution
其它：plan desire idea necessity preference等名词的表语从句和同位语从句, 其谓语动词要用虚拟语气的结构"(should)+动词原形" 。例如:
We all agreed to his suggestion that we(should)go to Beijing for sightseeing. My idea is that he (should)do exercises first. 3. 含蓄条件句
在某些虚拟语气结构中没有if 条件句, 虚拟条件是用其它形式表示出来, 这种现象在语法上称为" 含蓄条件" 。含蓄条件具体分为以下几种情况:
1) 通过动词不定式短语表示条件。例如: Y ou would be a fool to refuse his offer.
(=If you should refuse his offer,you would be a fool.) 要是你拒绝他的建议, 就太傻了。
2) 通过介词短语表达条件。
要不是那场暴雨, 我早就到达了。
3) 通过连词: She came to town yesterday,otherwise/or I would not have met her. 昨天她到城里来了, 不然我就不会遇见她了。
(otherwise/or=if she hadn't come)
I would have attended the meeting,but I have been too busy.(=...if I had not been too busy) 我本来要参加会议的, 只是太忙了。
4) 通过Were it not for...或Had it not been for...等句式表达条件。意为" 如果当时没有……",表示同过去事实相反的假设。例如:
Were it not for(=If it were not for) the leadership of the Party,we could not live a happy life. 要不是党的领导, 我们不可能过幸福生活。 (与现在事实相反)
Had it not been for(=If it had not been for) the leadership of the Party,we should have failed. 若不是有党的领导, 我们早就失败了。 (与过去事实相反)
5) 通过分词短语表达条件。例如:
Given more attention,the trees could have grown better.倘若给予更多的关心, 这些树本来可以生长得更好的。 (=If they had been given more attention...) :
Such mistakes could have been avoided.这种错误本来可以避免的。
(暗含条件从句if we had been more careful)
It was so quiet,you could have heard a pin drop.是那样的安静, 掉根针你都听得见。 (暗含条件从句if it had dropped to the ground)