单选题 The TCP/IP stack is a complete set of networking protocols.The OSI Model was meant to be a standardized way of connecting devices together,and most protocols have some direct correlation to the OSI Model.The OSI Model has 7 layers,the fourth layer is called________.

A、 physical layer
B、 data link layer
C、 application layer
D、 transport layer

【正确答案】 D

【答案解析】 TCP/IP协议栈是一种网络协议实现。OSI模型是用来进行设备间连接标准化的一种模型。OSI模型包含7层，第四层是传输层。