For an investment portfolio, the coefficient of variation of the returns on the portfolio is best described as measuring:（）

A. risk per unit of mean return.

B. mean return per unit of risk.

C. mean excess return per unit of risk.

30岁农民，头晕乏力，粪中钩虫卵（＋＋＋），血红蛋白60g／L，治疗应是（）

A.驱钩虫

B.驱钩虫加口服铁剂

C.驱钩虫加注射右旋糖酐铁

D.输血加注射右旋糖酐铁

E.口服叶酸或注射维生素B