Final answer:
A decrease in the price of good x results in fewer units of good y being sold, indicating that x and y are complementary goods.
Step-by-step explanation:
The scenario given suggests that a decrease in the price of good x leads to a decrease in the quantity demanded of good y. This indicates that goods x and y are complementary goods. Complementary goods are goods that are consumed together, where a change in the price of one good affects the demand for the other good in the opposite direction.
For example, if the price of movie tickets (good x) decreases, people may be more inclined to purchase theater snacks (good y). However, if the price of movie tickets increases, people may choose to attend fewer movies and therefore consume fewer theater snacks.
Therefore, the correct answer is c. complementary goods.