单项选择题
A.20 B.30 C.40 D.50
A.1.5cm2/kv B.1.6cm2/kv C.1.7cm2/kv D.1.8cm2/kv
A.600m B.800m C.900m D.1000m
A.2kv B.3kv C.l0kv D.35kv
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