2) Which one of below best represents the efficient frontier

A) the portion of the minimum-variance portfolio that lies above the global minimum variance portfolio.

B) the portion of the minimum-variance portfolio that represents the highest standard deviations.

C) the portion of the minimum-variance portfolio that includes the portfolios with the lowest standard deviation.

D) the set of portfolios that have zero standard deviation.

6) 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 a(n) _____ rate of return.

A) 8.5%

B) 9.0%

C) 8.9%

D) 9.9%

and also please explain the what are the major problems of Markowitz also called Mean-Variance portofolio optimization model.