The correct answer is: C. The price of either good falls.
An indifference curve is a graph that shows all the combinations of goods that a consumer is indifferent between. A budget line is a graph that shows all the combinations of goods that a consumer can afford with their given budget.
When the price of either good falls, the consumer’s budget line will shift outward. This is because the consumer can now afford to buy more of both goods. The consumer will then move to a higher indifference curve, which represents a higher level of satisfaction.
Option A is incorrect because a decrease in budget will cause the budget line to shift inward, and the consumer will move to a lower indifference curve.
Option B is incorrect because an increase in the price of only the goods measured along the Y-axis will cause the budget line to rotate around the point where it intersects the Y-axis. The consumer will then move to a lower indifference curve.
Option D is incorrect because an increase in the price of either good will cause the budget line to shift inward, and the consumer will move to a lower indifference curve.