单项选择题
A.L1~3前支 B.L2~4前支后股 C.L2~4前支前股 D.L3~4前支后殷 E.L3~4前支前股
A.30% B.40% C.50% D.60% E.70%
A.K+ B.Na+ C.Ca2+ D.Mg2+ E.Fe2+