—Let's go singing tonight?

—Sorry, I _____. I have to look after my sister. [ ]

A. mustn't

B. may not

C. can't

D. needn't

生物利用度研究最常用的方法是

A．药理效应法
B．体液药物浓度法
C．尿药浓度法
D．血药浓度法
E．组织药物浓度法