as as 的用法什么时候第二个as后面加人名,什么时候加句子.比如是He plays the piano as wel

as as 的用法
什么时候第二个as后面加人名,什么时候加句子.比如是
He plays the piano as well as mary 还是He plays the piano as well as Mary do?不要只说答案,介绍下用法,

He plays the piano as well as Mary does,前一个as是副词,后一个as是连词,引导比较状语从句,所以比较的东西应该是一样的.不能够拿he plays the piano跟Mary作比较.直接加人名的情况,比如说：She is as beautiful as her sister.
as可以作连词、介词及关系代词.现将其用法小结如下:
一、 as作连词的用法:
1. 作"当……的时候",引导时间状语从句.注意与when、 while的用法区别.
① when作"当……的时候"解,可以指较短的(一点)时间,也可指一段时间.如:
When he was at college, he could speak several foreign languages.
When the clock struck twelve, all the lights in the street went out.
② while常表示一段较长的时间或一个过程,强调主句谓语动词与从句谓语动词同时发生.如:
Work while you work. Play while you play.
③ 但属下列情形时,只用as, 而不用when或while.
A) 用于表示同一个人的两种动作交替进行,指"一边……,一边……".如:
The girl dances as she sings on the stage.
He looked behind from time to time as he went forward.
B)表示两个同步发展的动作或行为,译为"随着……".如:
As time went on / by, she became more and more worried.
As children get older, they become more and more interested in the things around them.
C)表示两个短促行为或事件几乎同时发生.如:
I thought of it just as you opened your mouth.
Just as the flying worm hit her face, she gave a loud cry.
D) 后接名词表示某一年龄段时,用as.如:
As a young man, he was active in sports.
2. as=since, 作"既然"、"由于"解,引导原因状语从句,常用来表示已为人们所知或显而易见的原因或理由.如:
As / Since you're not feeling well, you may stay at home.
As he wasn't ready in time, we went without him.
3. as=in the way that, 作"像"、"按照……的方式"解,引导方式状语从句.如:
He speaks English as Americans do.
Remember, you must do everything as I do.
4. 用于as...as...或not so/ as...as...中,前一个as是副词,后一个as是连词,引导比较状语从句.如:
They helped the old man as often as possible.
I don't speak English so/ as well as he does.
5. 作"虽然"、"尽管"解,引导让步状语从句.常用倒装语序,即adj. /adv. / n.+ as +主语+谓语+主句.如:
Tired as they were, they walked on.
Child as he is, he knows a lot. (child前不用冠词)
二、 as作关系代词,引导定语从句,作"正如"、"这一点"解.如:
He is very careful, as his work shows.
As is well-known, Taiwan belongs to China.
as的这种用法,请看2001年的高考题:
is known to everybody, the moon travels round the earth once every month.
A. It B. As C. That D. What
字母下划横线的为正确答案)
另外,当先行词被the same, such等词修饰时,常用as来引导定语从句.如:
Such a clever boy as he can learn anything quickly.
I was reading the same book as he bought yesterday.
三、 as作介词的用法:
as引导的介词短语大多用作状语,as译为"作为";少数情况可引起宾语补足语.如:
As a League member, I'll take the lead in everything. (状语)
She works as a doctor. (状语)
They have me as one of their own children.(引起宾语补足语)