单项选择题
A.1MΩ B.2MΩ C.2000MΩ D.20000MΩ
A.0.22dB/km和0.36dB/km B.0.36dB/km和0.22dB/km C.都为0.22dB/km D.都为0.36dB/km
A.ρ10<100Ω.m B.ρ10<200Ω.m C.ρ10<500Ω.m D.ρ10>500Ω.m
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