单项选择题
A.DC1600V B.DC1700V C.DC1800V D.DC1900V
A.815±10 B.870±10 C.880±10 D.890±10
A.≤5% B.≤10% C.≤20% D.≤30%
A.R=50m B.R=100m C.R=150m D.R=250m
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