【C17】A．ringB．replyC．answerD．respond

A．Leaving it alone.B．Sitting down.C．Trying to find an answerD．Asking the teacher.

【C2】A．additionB．replyC．turnD．return

【C3】A．partB．pointC．answerD．solution

While I _____ television, the door bell _____.A. watched／would ringB. would watch／h

PPP会话阶段属于链路维护报文的有（)A.Echo－RequestB.Echo－ReplyC.Config－RequestD.Config－Nak

PING命令使用ICMP的哪一种code类型：（ ）A.RedirectB.Echo replyC.Source quenchD.Destination Unr