The telephone,_____was invented by Alexander Graham Bell.
A.as is known by us        B.which we know   C.as we know it            D.as we know。老師給的答案是C，解釋是as we know it是一個方式狀語從句，但我不知道為什么其他三個選項是錯的或者是不恰當的，請老師解惑，謝謝！

此題的逗號究竟在哪兒？

The telephone，_____，was invented by Alexander Graham Bell.
A.as is known by us        B.which we know   C.as we know it            D.as we know

上空選D為妥，AS引導非限定性定語從句。

The telephone_____was invented by Alexander Graham Bell.
A.as is known by us        B.which we know   C.as we know it            D.as we know

此空選C為妥，AS引導方式狀語從句。

原題只有The telephone后有一個逗號，請問選哪個恰當？為什么其他三個不恰當？請“qinjianyu”解釋一下，謝謝你！

以此為例：

The telephone，_____，was invented by Alexander Graham Bell.
A.as is known by us        B.which we know   C.as we know it            D.as we know

A.因為know通常不用于被動語態，所以其中介詞BY有問題，如果換成as is known to us或者as is known都正確。

B.which代替整個主句習慣上應放在句未，故其正確形式：The telephone was invented by Alexander Graham Bell,which we know.

C.as we know it是對as前面的名詞的限定，一般不用逗號隔開，故不妥。

以上是個人見解，希望能夠幫到你。