问题如下：
Based on below table, the target semideviation for the portfolio is closest to:
选项：
A.2.78%
B.3.68%
C.4.35%
解释：
B is correct. The target semi-standard deviation or target semideviation is the denominator of the Sortino ratio. The numerator of the Sortino ratio is the average portfolio return minus the target rate of return
(minimum acceptable return, or MAR).
Sortino ratio = (Average portfolio return - MAR) / Target semideviation
Substituting the values provided in Exhibit 1, the target semideviation is as follows:
Target semideviation= (8.20% - 5.00%) / 0.87 = 3.678% = 3.68%
老师请问，这里面的reture大于了MAR，ratio为何不是0呢？不是只算小于MAR的部分吗？ min（r-rT，0）
