单项选择题
A.酸性B.碱性C.中性D.强酸性
A.1-2mB.3-4mC.4-6mD.5-7m
A.0.2-0.4mg/LB.0.6-0.8mg/LC.0.5-0.7mg/LD.0.6-0.9mg/L