A.≥98% B.≥98.5% C.≥99% D.≥99.5%
A.≤20µg/L B.≤20mg/L C.≤25µg/L D.≤15µg/L
A.≤0.002mol/l B.≤0.003mol/l C.≤0.005mol/l D.≤0.05mol/l