單項(xiàng)選擇題按照相關(guān)規(guī)定:當(dāng)采用專線通信時(shí),從故障點(diǎn)到維護(hù)中心的響應(yīng)時(shí)間應(yīng)不大于()

A.10s
B.20s
C.30s
D.60s


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