1. [单选题]OSI七层模型中，“包”是哪一层数据封装的名称（）
A. 物理层
B. 数据链路层
C. 网络层
D. 传输层
2. [单选题]While troubleshooting a connectivity problem on the network, you issue the ping command from your PC command prompt, but the output shows "request times out."At which OSI layer is this problem associated with?
A. The data link layer
B. The application layer
C. The access layer
D. The session layer
E. The network layer
