单项选择题
A.70~100mg/LB.100~500mg/LC.500~700mg/LD.700~900mg/L
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