单项选择题
A.小于0.1uS/cmB.0.5-2uS/cmC.2-4uS/cmD.50-500uS/cm
A.加酸至pH<2后蒸馏B.加亚硫酸钠后蒸馏C.加热煮沸10minD.加碱性高锰酸钾后蒸馏
A.2:1B.1:10C.2.5:1D.1:2