If given the standard deviations of the returns of two assets and the correlation between the two assets, which of the following would an analyst NOT necessarily be able to derive from these The:（）

A. covariance between the returns.

B. expected returns.

C. variance of each return.

一级动力学消除的特点有（）

A.半衰期与血药浓度无关

B.半衰期与血药浓度有关

C.单位时间消除药量等比

D.单位时间消除药量等差

E.连续给药5个半衰期达稳态血药浓度（C_ss）