一、 单选题,每题仅一个正确答案,每题1.5分,共30分: 1. Which is not a network communication links?D.Subway 2.Which is not the types of protocol data unit in TCP/IP?C.datetime 3.In which state the delays of router become small?A. La/R 0 4.When congest occur in network, which delay become large?B.queuing delay 5.Application protocol define the types of messages exchanged, which are: A.request & response messages 6.Which version of hypertext transfer protocol ar