--- What        it be?

--- It         be a man, for it is not moving. It      be a dustbin, I think.

A．can, may, must

B．can, can’t, must

C．can, must, can

D．may, may not, could

快速以太网要求网卡自动协商过程在（）内完成。

A．10ms

B．50ms

C．100ms

D．500ms