According to the mean-variance criterion, which one of the following investments dominates all others? Select one: O a. E(r) = 0.15; Variance = 0.20 b. E(r) = 0.10; Variance = 0.20 c. E(r) = 0.10; Variance = 0.25 d. E(r) = 0.15; Variance = 0.25 e. None of these options dominates the other alternatives