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.

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:
Option A:expected return.
Option B:indifference curve.
Option C:capital allocation line slope.

Answer: B