Answer:
d. An index fund with beta = 1.0 should have a required return of 11%.
Explanation:
required rate of return for a market indexed portfolio = 6% + (1 x 5%) = 11%
If the required rate of return is less than 11%, the beta is lower than 1.
If the required rate of return is more than 11%, the beta is larger than 1.
If beta doubles, then the required rate of return = 6% x (2 x 5%) = 16%