Given a text T, and several options, according to the question posed in the text T to choose the most appropriate option from the options as the answer, please directly output the most appropriate option, do not need to output the explanation.

Which of the following statements is least accurate? The efficient frontier is the set of all attainable risky assets with the:
Option A:highest expected return for a given level of risk.
Option B:lowest amount of risk for a given level of return.
Option C:highest expected return relative to the risk-free rate.

Answer: C