Consider a treasury bill with a rate of return of 5% and the following risky securities: security a: e(r) = .15; variance = .0400 security b: e(r) = .10; variance = .0225 security c: e(r) = .12; variance = .1000 security d: e(r) = .13; variance = .0625 the investor must develop a complete portfolio by combining the risk-free asset with one of the securities mentioned above. the security the investor should choose as part of her complete portfolio to achieve the best cal would be
a. a
b. b
c. c
d. d

Stocks a, b, and c are similar in some respects: each has an expected return of 10% and a standard deviation of 25%. stocks a and b have returns that are independent of one another; i.e., their correlation coefficient, r, equals zero. stocks a and c have returns that are negatively correlated with one another; i.e., r is less than 0. portfolio ab is a portfolio with half of its money invested in stock a and half in stock b. portfolio ac is a portfolio with half of its money invested in stock a and half invested in stock c. which of the following statements is correct? a. portfolio ab has a standard deviation that is greater than 25%.b. portfolio ac has an expected return that is less than 10%.c. portfolio ac has a standard deviation that is less than 25%.d. portfolio ab has a standard deviation that is equal to 25%.e. portfolio ac has an expected return that is greater than 25%.