---- What do you think of the lecture made yesterday?

---- Excellent! _______ you missed such a wonderful lecture?

A．How is it that

B．Why it was that

C．How was it that

D．When was it that

TCP/IP是一个协议族，它的体系结构分4层：应用层、网际层、网络接口层和 (46) ，其中ARP协议属于 (47) 。为了在源主机和目的主机之间传送数据，IP协议需要确定源主机和目的主机是否在同一个网络中。

A．会话层

B．传输层

C．网络层

D．表示层