In the Characteristic Selectivity $($CS$)$ performance measure, a$.$ portfolio performance is measured by comparing the returns of each stock in the portfolio to the return of a benchmark portfolio. b$.$ portfolio performance is measured on the basis of return per unit of risk. c$.$ portfolio performance is measured by assessing the quality of services provided by money managers by looking at adjustments made to the content of their portfolios. d$.$ portfolio performance is measured on the basis of historic average differential return per unit of historic variability of differential return. e$.$ portfolio performance is measured by examining both unsystematic and systematic risk.