In a return-standard deviation panel, which of the following statements is (are) true for risk- averse investors? (The vertical and horizontal lines are referred to as the expected return-axis and the standard deviation-axis, respectively) 1) An investor's own indifference curves might intersect. II) Indifference curves have negative slopes. III) In a set of indifference curves, the highest offers the greatest utility. IV) Indifference curves of two investors might intersect. O a. I and Il only O b. II and III only O c. I and IV only O d. III and IV only