单项选择题
A.20~30g/LB.30~50g/LC.50~70g/LD.70~90g/L
A.30~80g/LB.40~90g/LC.50~100g/LD.60~110g/L
A.5~10g/LB.10~15g/LC.15~20g/LD.20~25g/L