The correct answer is C. Both demand and supply.
In a free market, the price of a product is determined by the interaction of supply and demand. Supply is the amount of a good or service that producers are willing and able to offer for sale at various prices. Demand is the amount of a good or service that consumers are willing and able to purchase at various prices.
The price of a product will tend to rise when demand is high and supply is low. This is because when demand is high, consumers are willing to pay more for the product. When supply is low, producers are not able to meet the demand for the product, so they can charge a higher price.
The price of a product will tend to fall when demand is low and supply is high. This is because when demand is low, consumers are not willing to pay as much for the product. When supply is high, producers are able to meet the demand for the product, so they have to lower their prices in order to sell their products.
The government can influence the price of a product through taxes, subsidies, and regulations. However, the government cannot control the price of a product in a free market. The price of a product is determined by the interaction of supply and demand.