— Do you suppose you could do it without help, Jack?

— ______.This is not the first time for me. [ ]

A. Not likely.

B. Not exactly

C. Don't worry.

D. I'm afraid not.

下列哪些网络设备的各个端口需要装配MAC地址？（）

A.主机

B.集线器

C.交换机

D.路由器