1. [多选题]The LAN needs are expanding at the Ezonexam corporate office, which is quickly growing. You are instructed to enlarge the area covered by a single LAN segment on the Ezonexam network.Which of the following are layer 1 devices that you can use? (Choose all that apply.)
A. A switch
B. A router
C. A network adapter card
D. A hub
E. A repeater
2. [多选题]As the Ezonexam network administrator, you are required to have a firm understanding of the OSI model. Why does the data communication industry use the layered OSI reference model? (Choose two)
A. It enables equipment from different vendors to use the same electronic components, thus saving research and development funds
B. It encourages industry standardization by defining what functions occur at each layer of the model
C. It divides the network communication process into smaller and simpler components; thus aiding component development, design and troubleshooting
D. It provides a means by which changes in functionality in one layer require changes in other layers
E. It supports the evolution of multiple competing standards and thus provides business opportunities for equipment manufacturers
3. [单选题]IP地址为：192.168.50.70，掩码为：255.255.255.248，则该IP和掩码结合，共划分了多少个子网（不包括全0子网和全1子网）（）
A. 8
B. 30
C. 6
D. 14
4. [多选题]下列哪一设备工作时，要用到OSI的七个层（一层到七层）（）
A. PC
B. 网管机
C. WEB服务器
D. 交换机
E. 路由器
5. [单选题]PPP工作在OSI的哪一层（）
A. 物理层
B. 数据链路层(data link layer)
C. 网络层
D. 传输层
