单项选择题

A.[Ca]·[P]=6.25~7.50(25~30)
B.[Ca]·[P]=8.75~10(35~40)
C.[Ca]·[P]=11.25~12.50(45~50)
D.[Ca]·[P]=13.75~15(55~60)
E.[Ca]·[P]=16.25~17.50(65~70)