下列哪项不是WHO癌痛药物治疗的主要原则（）.

A.口服给药

B.按需给药

C.按时给药

D.按阶梯给药

E.用药应个体化

He bought some books in the bookstore and his father________ him a lot of money.

A．gives

B．will give

C．ought to give

D．must have done