The Cross-Price Elasticity of Demand Between Goods X and Y

The cross-price elasticity of demand between goods X and Y

A) measures the responsiveness of the quantity of X demanded to changes in the price of Y.
B) is the percentage change in the price of Y divided by the percentage change in the quantity of X demanded.
C) is greater than zero if X and Y are substitutes.
D) both a and c
E) all of the above