A.大于等于50kV B.大于等于60kV C.大于等于70kV D.大于等于80kV
A.大于等于30kV B.大于等于40kV C.大于等于50kV D.大于等于60kV
A.大于等于20kV B.大于等于25kV C.大于等于30kV D.大于等于35kV