A.≥0.5MPa B.≥0.6MPa C.≥0.7MPa D.≥0.8MPa
A.≥0.15MPa B.≥0.2MPa C.≥0.23MPa D.≥0.25MPa
A.小于1000V B.大于1000V C.1000V以下 D.1000V以上