Answer:
C.
Explanation:
The law of demand states that when the price of a good or service increases, the quantity demanded decreases and when the price decreases the quantity demanded increases (other things constant).
Is not option A because it says changes in income and not changes in prices. Is not option B because it says the opposite that the law of demand states: when the muffins price is low, Melissa buys fewer than when the price is high. Is not option D because the law of demand is not directly related with substitute goods. It is option C because when the price is low ($0.25) Dave buys more donuts than when the price is high ($0.50)