Answer:
The correct answer is: price.
Step-by-step explanation:
The demand law studies the relationship between the quantity demanded of a good or service and its price. That relationship is inversely proportional. It means if the quantity demanded increases the price will decrease. Besides, if the quantity demanded decreases the price will increase.
Plotted in a graph, the demand curve will only respond to changes in price. The demand slope will move rightwards or leftwards according to the case.