In the following narrative about the CSMA/CD protocol, the error one is（）
A. Suitable for wireless networks for wireless link sharing
B. Send data frames while detecting conflicts
C. Minimum frame length needs to be limited based on network span and data transfer rates
D. When the signal propagation delay approaches 0, the channel utilization rate approaches 100%
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The physical and logical topology of Ethernet using a single hub is（）and（）respectively
A. Star topology, Bus topology
B. Star topology, Ring topology
C. Bus topology, Star topology
D. Tree topology, Bus topology
Before communication, the exchange mode that needs to establish physical connection between the sender and the receiver is（）
A. Circuit switching
B. Message exchange
C. Packet switching
D. Store and forward exchange
Among the following factors, the channel data transmission rate will not be affected（）
A. Signal propagation speed
B. Signal to noise ratio
C. Bandwidth
D. Modulation rate
Compared with multimode fiber, the main characteristics of single-mode fiber are（）
A. Long transmission distance, high cost and thin core
B. Long transmission distance, high cost and thick core
C. Short transmission distance, low cost and thick core
D. Short transmission distance, low cost and thin core
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