After ( ) the meeting room and he took the seat ( ) is freeA.entering into,which B.he entered into,where C.entering,that D.he entered,in which 我想不通,为什么不是C呢?

After ( ) the meeting room and he took the seat ( ) is freeA.entering into,which B.he entered into,where C.entering,that D.he entered,in which 我想不通,为什么不是C呢?
After ( ) the meeting room and he took the seat ( ) is free
A.entering into,which B.he entered into,where C.entering,that D.he entered,in which 我想不通,为什么不是C呢?

After ( ) the meeting room and he took the seat ( ) is freeA.entering into,which B.he entered into,where C.entering,that D.he entered,in which 我想不通,为什么不是C呢?
首先and连接的两句话必须各自都得有主语,另外take in a seat 是固定搭配,后面的is free修饰前面的seat ,用which 来引导,介词一般就要放在连接词which前面.

and连接两个相同的成分，take in a seat 固定搭配

and连接了两个句子，前一句就少了主语 enter又是及物动词

不可能是D。