单项选择题
A.老年 B.中年妇女 C.中年男子 D.儿童 E.婴儿
A.1~2mm B.2~4mm C.3~4mm D.4~5mm E.4~6mm
A.5%~10% B.10%~20% C.20%~40% D.30%~50% E.40%~60%