He is good at English we all know. A. that B. as C. whom D. what

问题补充：

He is good at English, we all know.

A. that

B. as

C. whom

D. what

答案：

A. that

B. as

C. whom

D. what

解析：as作关系代词可以单独用来引导非限制性定语从句。这时as所指代的不是主句中某个名词，而往往指代整个主句的含义。as在从句中可以作主语、宾语。从句可放在主句后，也可置于主句前。在本句中,as作宾语.