问题
单项选择题
When a risk-free asset is unavailable, the optimal portfolio on an efficient frontier for each investor is represented by the:（）
A. market portfolio.
B. utility curve that intersects the efficient frontier.
C. highest utility curve that is tangent to the efficient frontier.
答案
参考答案：C
解析：
In the absence of a riskless asset, the optimal portfolio for an investor is the point of tangency between the efficient frontier and the highest possible indifference curve for the investor.