Final answer:
An investor who is indifferent to risk would have a horizontal indifference curve, representing an equal valuation of all portfolios with a given expected return, regardless of their risk.
Step-by-step explanation:
An investor who is indifferent to risk would be represented by a horizontal indifference curve. This implies that the investor values all portfolios with a given expected return equally, regardless of the risk. Typically, indifference curves are downward sloping and convex concerning the origin, indicating a tradeoff between goods to maintain the same level of utility (as seen in the typical preferences for consuming goods like books and doughnuts, where increasing the quantity of one good requires a reduction in the other to remain on the same curve).
However, in the context of an investor indifferent to risk, the indifference curve would not slope downward since the investor does not require a higher expected return to compensate for higher risk, which is an exception to the typical shape of indifference curves. The horizontal shape of the investor's indifference curve illustrates that the investor values expected return only and is not concerned with the level of risk associated with the portfolio.