For Two Goods,X and Y,to Be Classified as Substitutes,it Must

For two goods,X and Y,to be classified as substitutes,it must be the case that

A) X and Y are identical.
B) consumers tend to purchase both items.
C) when the price of X rises,the demand for Y decreases.
D) when the price of X rises,the demand for Y increases.
E) X and Y look alikE.