Question

两道英语题 高中

tom， you played so well .but,i ____ you played the paino.
A did not know B had not known
解释加答案啊~

it is well known和 what is well known 和as is well known的用法和区别
稍微的解释一下，不要百度百科！！
谢谢~

Answer 1

B
tom是过去某天弹了，弹得很好，
而我在tom弹之前，是不知道tom会弹。
应该是用过去完成时

三个差不多吧，就是用起来时语法结构不同，所以有点不同。
it is well known 后面加从句才完整，是使用it作形式主语的主语从句。一般是加that引导的从句
what is well known 不是很清楚，个人感觉没这么种用法。如果有这种用法的话，估计和前面差不多，不过是主语从句的引导词不同吧，后面也要加从句。
as is well known就是个插入语，就和中文的 众所周知 一样，后面直接说明就好了。

Answer 2

B 考点：过去完成时，要点 要找到过去的一个点，过去完成时的意思是过去的过去。就是说you played so well 这是过去的一个点，在这个点之前我还不知道，用B

It is well known+that
what is well known+is（that）
as is well known ，+完整句子

例
It is well known+that Tom is handsome
what is well known+is（that）Tom is handsome
as is well known ，Tom is handsome

Answer 3

B
played是过去时态，“我不知道Tom弹钢琴”是“Tom弹得很好”之前的事，过去的过去，用过去完成时。
说一下那3个的用法（3者意思是一样的）
it is well known：It is well known that……（什么什么是众所周知的）是主语从句用法
what is well known is that……也是主语从句，what指代省略号
as is well known一般用于句首，或者插入语（不影响句子成分）
As is well known,he is naughty.
=He,as is well known,is naughty.
as is well known一般不用，用as is known to (us) all比较多

Answer 4

A
did not know 指过去不知道
had not known不仅指过去不知道，还包括现在也不知道
“you played so well ”说明现在已经知道

be well known to sb. 为某人所熟知
be well known for sth. 因为什么而出名
be well known as sth. 作为什么而出名

it is well known和 what is well known 和as is well known
它们本质上没多大区别

Answer 5

A.过去不知道。很显然，选择题是对话B答案过去完成不会出现在对话中。
be well known to sb. 为某人所熟知，to,对于其他人
be well known for sth. 因为什么而出名 ，for表示原因，语气轻
be well known as sth. 作为什么而出名，AS作为。

都是众所周知意思，真的没什么太大区别，非说有，那么
it is well known 习惯用语。常放在句首。
what is well known引导主从句
as is well known 常放在句中。