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：
After singing some songs，the competitors danced onto the green field，waving their arms in the air as if they were eagles.
(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.
The milk smells as if it is sour.
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.
He acted as if he had lost the job yesterday.
I heard it is because children are lighter and the horses can run faster and farther.
(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.
because, why, that引导表语从句
This/That/It is because...
This is because I'm very busy.
This/That/It is why...
This is why I'm very busy.
The/A/One reason (for/for which/why...)
The reason why I'm busy is that time is limited.
They’ve been riding horses all their lives.
(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.
They have built a house.(完成)
They have been building a house.(尚未完成)
Have you been meeting him recently?
Have you met him recently?
I have been waiting for you for two hours.
I have waited for you for two hours.
Who has been eating these oranges?
Who has eaten these oranges?
—Why are you looking a bit tired?
—I have been cleaning the house.
1．The boy was lying on the bed if he was sleeping.
2．He was late for school.That was he got up late.
3．Both of them (live) happily since then.
4．I (teach) English for more than twenty years.
5．One reason for her preference for city life is she can have easy access to places like shops and restaurants.
6．The teacher treats his students as if they (be) his children.
1．The competition attracted 400 students (represent) 35 different countries and it proved to be a great success.
2． (absolute), what she's just said is the very idea that I want to express.
3．Her business was so successful that Maric was able to set up new (branch) elsewhere.
4．Bill Gates has donated (捐赠) a large sum of money to society. And he is highly (respect) for his donation.
5．Only when we match our words with actions can we make difference in whatever we hope to accomplish.
6．On arriving in the tsunamistricken island, they set to rescue the people there.
7．In order to save the animals out of danger, they set a special place for them to live freely.
8．We were about to set on our way when it suddenly began to rain.
9．She treats him as if he (be) a stranger.
10．As a senior high school student，I (learn) English for ten years.