单项选择题
A、有防爆标志,无防爆合格证号 B、有防爆合格证号,无防爆标志 C、有防爆标志,有防爆合格证号 D、无防爆标志,无防爆合格证号
A.2%B.3%C.5%D.6%
A.200mm B.300mm C.500mm D.1000mm