According to the mean-variance criterion, which one of the following investments is dominated by all others? O E(t)=0.10; Variance=0.20 O E[r]=0.20; Variance=0.2 E(r)=0.20; Variance=0.1 E{r=0.10; Variance=0.3 a O E[r]=0.05; Variance=0.3