【答案解析】[解析] 各年连续复利的股票报酬率分别为:ln[(25+1)/20]=26.24%;ln[(26+2)/25]=11.33%;ln[(30+1)/26]=17.59%;平均股票报酬率=(26.24%+11.33%+17.59%)/3=18.39%;报酬率的方差=[(26.24%-18.39%)×(26.24%-18.39%)+(11.33%-18.39%)×(11.33%-18.39%)+(17.59%-18.39%)×(17.59%-18.39%)]/(3-1)=0.5605%;
