Two goods are either substitute to each other or they are complement each other. If the price increase in one good (good X) causes consumers to use other good (good Y) in place of this good, we say that these two goods (X and Y) are substitutes for each other. Substitutes are goods that are generally used in place of one another. Concerning the substitute goods, a price increase in good X leads to quantity demanded of good Y to increase. Goods have also complementary relationship. Complements are goods that are typically used together. One good or service cannot be used without the other. Concerning the complements, price increase of good X causes quantity demanded in good Y to decrease. The correct answer is D.