1. [单选题]OSPF骨干区的区域编号为（）
A. 0.0.0.1
B. 255
C. 0.0.0.0
D. 255.255.255.255
2. [单选题]为了连接“帧中继”线路，网络中的路由器需要提供的端口类型为（）
A. FastEthernet
B. Serial
C. BRI
D. Ethernet
3. [多选题]When you compare the differences between half-duplex and full-duplex Ethernet, which of the following characteristics are exclusive to half-duplex? (Select two answer choices)
A. Half-duplex Ethernet operates in a shared collision domain.
B. Half-duplex Ethernet operates in an exclusive broadcast domain.
C. Half-duplex Ethernet has efficient throughput.
D. Half-duplex Ethernet has lower effective throughput.
E. Half-duplex Ethernet operates in an exclusive collision domain.
