Final answer:
The correct answer is the law of supply, which shows a positive relationship between price and quantity supplied, with other factors remaining the same.
Step-by-step explanation:
The correct answer to the question is A. supply. The law of supply states that there is a positive relationship between price and the quantity supplied, ceteris paribus, which means 'all other things being equal'. In economic terms, this means that as the price of a good or service increases, sellers are more willing to provide a greater quantity of that good or service. Conversely, if the price decreases, sellers will be less willing to supply much of it. This is because higher prices can lead to greater profits, which incentivizes producers to increase production.