The police were seeking more information to find out ________ the rich merchant.

A．who was it that killed

B．who it was that killed

C．it was who killed

D．who was it killed

生物滤池的布水设备应使污水能（）在整个滤池表面上。布水设备可采用活动布水器，也可采用固定布水器。

A.集中分布

B.不集中分布

C.不均匀分布

D.均匀分布