Many lifestyle patterns do such ________ great harm to health that they actually speed up ________ weakening of the human body．[ ]

A．a；/  

B．/；the  

C．a；the  

D．/；/

在实务中衡量投资组合风险最常用的指标是()。

A．收益额

B．期望收益率

C．方差

D．协方差