as though/as if句式等重点句型详解

as though/as if句式等重点句型详解知识点包括as though/as if句式、because, why, that引导表语从句、现在完成进行时和现在完成时等部分，有关as though/as if句式等重点句型详解的详情如下：

as though/as if句式

After singing some songs，the competitors danced onto the green field，waving their arms in the air as if they were eagles.

唱完歌曲后，选手们在绿色的场地上跳舞，在空中挥舞着胳膊，就像是老鹰一样。

(1)句式分析：这是一个主从复合句。主句是the competitors danced onto the green field，waving their arms in the air是现在分词短语作伴随状语，as if they were eagles是方式状语从句。

(2)as if 意为“好像，仿佛”，相当于as though，在此引导方式状语从句。as though/as if 后面可接从句(状语从句或表语从句)、形容词、介宾短语、现在分词、动词不定式等。as if/as though 引导的从句常有两种情况：

①若as if/as though 引导的从句表示的是事实或很可能出现的情况，从句一般用陈述语气。

It looks as if/as though our side is going to win.

看来我方要赢了。

The milk smells as if it is sour.

牛奶闻起来好像酸了。

②若as if/as though 引导的从句表示的是非真实情况或出现的可能性不大的情况，从句通常用虚拟语气。不同虚拟情况下从句谓语动词的形式为：

 

 

He talks as if he knew all about it.

他谈起来好像完全知道这件事似的。

He acted as if he had lost the job yesterday.

昨天他表现得好像丢了工作一样。

because, why, that引导表语从句

I heard it is because children are lighter and the horses can run faster and farther.

我听说这是因为孩子们更轻，马跑得更快更远。

(1)句式分析：这是一个主从复合句。主句是I heard，后面是省略了that的宾语从句，在宾语从句中又包含了because引导的表语从句。

(2)This/That/It is because...表示“这/那是因为……”，because引导表语从句，从句表示原因，this/that/it表示结果。如：

He wouldn't like to go out; this is because he doesn't feel well.

他不想出去，这是因为他觉得不舒服。

[易混辨析]

because, why, that引导表语从句

连接词	常用句型	例句
because	This/That/It is because... 这/那是因为……	This is because I'm very busy. 这是因为我很忙。
why	This/That/It is why... 这/那就是为什么……	This is why I'm very busy. 这就是为什么我很忙。
that	The/A/One reason (for/for which/why...) is that...(……的)原因/一个原因是……	The reason why I'm busy is that time is limited. 我忙是因为时间有限。

现在完成进行时和现在完成时

They’ve been riding horses all their lives.

他们一生都在骑马。

(1)句式分析：这是一个简单句。主语是They，谓语是have been riding，宾语是horses。

(2)have been riding是现在完成进行时，表示从过去开始一直延续到现在，或将继续延续至将来。如：

We have been working on this project for over a month now.

到目前为止，我们一直从事这个项目，已经一个多月了。

[思维拓展]

现在完成进行时和现在完成时

(1)现在完成时表示已经完成，而现在完成进行时表示还没完成还要延续下去。试比较：

They have built a house.(完成)

They have been building a house.(尚未完成)

(2)现在完成进行时是由“have/has been＋doing”构成的，可表示动作的重复，而现在完成时一般不表示动作的重复。如：

Have you been meeting him recently?

你最近常和他见面吗？

Have you met him recently?

你最近见到过他吗？

(3)现在完成进行时有时含有感情色彩，而现在完成时一般是客观地讲述一个事实。如：

I have been waiting for you for two hours.

我一直等了你两个小时。(可能表示不满)

I have waited for you for two hours.

我等了你两个小时。(说明一个事实)

(4)现在完成进行时强调动作的延续性，而现在完成时强调结果。如：

Who has been eating these oranges?

谁一直在吃这些橘子呀？(可能还剩余一些)

Who has eaten these oranges?

谁把这些橘子吃了？(强调吃得一个不剩)

(5)如果强调某一动作刚刚结束，并已产生某种影响时，常用现在完成进行时。如：

—Why are you looking a bit tired?

——为什么你看起来有点儿累？

—I have been cleaning the house.

——我一直在打扫房子。