—Why did he say so?

—Sorry, I don’t understand        he has said means.

A．all what

B．what all

C．all that

D．that all

关于询问证人，下列哪一说法是错误的

A．询问证人应当个别进行

B．询问证人应制作笔录

C．询问不满18周岁的证人，应当通知其法定代理人到场

D．询问证人前，侦查人员必须出示侦查机关的证明文件