问题如下：
Which of the following performance measures is most appropriate for an investor who is not fully diversified?
选项：
A. M-squared.
B. Treynor ratio.
C. Jensen’s alpha.
解释：
A is correct.
M-squared adjusts for risk using standard deviation (i.e., total risk).
belta是系统性风险，系统性风险不是不能被diversified吗？
