The correct answer is B.
The market equilibrum is a combination of price and quantity at which the desires of producers and consumers coincide. The amount demanded (the amount of products and services that consumers want to purchase or can afford at $4) equals the quantity supplied (the amount of products and services that producers are willing to sell in the markets at $4). At equilibrium, markets clear, which means that their is shortage or surplus and the whole production is sold and allocated among buyers.
