After ( ) the meeting room and he took the sea ( ) is free.

After ( ) the meeting room and he took the sea ( ) 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?
which 的先行词是room?

就是D
总体看这个句子是用and连接的,and前后应该是相同的结构,后面是过去式前面就应是过去式,排除A和C,对于B和C,B中entered into重复,排除B
对于你说的C,就是关于怎样选择先行词的问题了,这句话的意思应该是:会议事里的茶是免费的所以用where/in which