31. Consider two perfectly negatively correlated risky securities A and B. A has an expected rate of return of 10% and a standard deviation of 16%. B has an expected rate of return of 8% and a standard deviation of 12%. The risk-free portfolio that can be formed with the two securities will earn rate of return. A. 8.5% B. 9.0% C. 8.9% D. 9.9%