Robert Only Consumes X and Y,and His Indifference Curves Have

Multiple Choice

Robert only consumes X and Y,and his indifference curves have the usual convex shape.Consider the consumption bundles (3,9) ,(6,6) ,and (9,3) (Hint: The consumption bundles completely exhaust Robert's income) .If Robert is indifferent between (3,9) and (9,3) ,then:

A) he prefers (3,9) over (6,6) .
B) he prefers (9,3) over (6,6) .
C) he prefers (6,6) over both (3,9) and (9,3) .
D) he prefers (6,6) over (3,9) but not over (9,3) .