单选题
When should Frequency Division Multiplexing be used?
A、
when the attenuation on a medium is greater than 25%.
B、
when the white noise on the medium exceeds 50% of the medium"s bandwidth
C、
when the achievable data rate of the medium exceeds the data rate of the digital signals to be transmitted
D、
when the useful bandwidth of the medium exceeds the required bandwidth of the digital signals to be transmited
【正确答案】
D
【答案解析】
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