1. [单选题]工作在OSI第三层(layer 3)的设备是：()
A. 网卡
B. 路由器
C. 交换机
D. 集线器
2. [单选题]What kind of cable should be used to establish a trunked line between two Catalyst switches?
A. A straight-through cable
B. An EIA/TIA-232 serial cable
C. An auxiliary cable
D. A modem cable
E. A cross-over cable
3. [多选题]Why is full-duplex Ethernet superior to its single-duplex counterpart? (Select two answer choices.)
A. It uses inexpensive hubs
B. It operates without collisions
C. It operates on switches
D. It provides faster data transfer
E. It utilizes fewer wiring pairs
