单项选择题
Which of the following layers of the TCP/IP model most closely corresponds to the network layer of the OSI model?（）
A.Application B.Internet C.Transport D.Network E.Data Link
多项选择题 Which three of the protocols below belong to the application layer?（）
多项选择题 Which three of the following OSI model layers also belong to the TCP/IP model?（）
单项选择题 Which one of the following is the most commonly used layer 2 network device?（）
