问题如下：
With respect to capital market theory, an investor’s optimal portfolio is the combination of a risk-free asset and a risky asset with the highest:
选项：
A. expected return.
B. indifference curve.
C. capital allocation line slope.
解释：
B is correct.
Investors will have different optimal portfolios depending on their indifference curves. The optimal portfolio for each investor is the one with highest utility; that is, where the CAL is tangent to the individual investor’s highest possible indifference curve.
Highest expected return 为什么是错的呀，再往上不就是不可达事件吗？感觉highest return好像也没问题呀