单项选择题
A.15% B.10% C.20% D.12%
A.5-6 B.6-8 C.5-7 D.6-7
A.交换性钾和非交换性钾 B.水溶性钾和缓效性钾 C.交换性钾和水溶性钾 D.交换性钾和缓效性钾