The correct answer is B. substitutes.
Substitutes are goods that can be used in place of each other. If the price of one good goes up, the demand for its substitute will go up, and vice versa. This is because consumers will switch to the substitute good in order to save money.
For example, if the price of coffee goes up, the demand for tea will go up. This is because coffee and tea are substitutes. Consumers will switch to tea in order to save money.
The cross-price elasticity of demand is a measure of how much the demand for one good changes in response to a change in the price of another good. The cross-price elasticity of demand is negative for substitutes. This means that if the price of one good goes up, the demand for its substitute will go up.
The other options are incorrect.
- Unrelated goods are goods that are not related to each other. If the price of one unrelated good goes up, the demand for the other unrelated good will not change.
- Complements are goods that are used together. If the price of one complement goes up, the demand for its complement will go down.
- Normal goods are goods that people demand more of when their income goes up.