【正确答案】 B

【答案解析】The coefficient of variation expresses how much dispersion exists relative to the mean of a distribution and allows for direct comparison of dispersion across different data sets. CV=[standard deviation of returns]/[expected rate of return] Portfolio 1: 9.7%/5.6%=1.73; Portfolio 2:17.4%/12.3%=1.41; Portfolio 3:20.9%/13.5%=1.55. We prefer lower CV, so portfolio 2.