单项选择题
A.500~1000mg/LB.450~950mg/LC.400~900mg/LD.350~850mg/L
A.0.5mmol/LB.1.0mmol/LC.1.5mmol/LD.2.0mmol/L
A.10-3~10-1mmB.10-4~10-2mmC.10-5~10-3mmD.10-6~10-4mm