Chris chooses between two goods, X and Y (see figure below). At first, the price of X is low and the price of Y is high (budget line B1). Chris tells you his best affordable combination of X and Y is at point A. Then the price of X rises, while the price of Y falls (budget B2). Chris tells you that at these new prices, his optimal consumption bundle is still point A. What must be true of Chris's preferences?
A) Chris prefers X to Y.
B) Chris prefers Y to X.
C) X and Y are perfect complements.
D) X and Y are perfect substitutes.
E) Chris's preferences must violate one of our assumptions about consumer behavior.