The Law of Supply states that, under the assumption of ceteris paribus, an increase in the price of a product leads to an increase in the quantity supplied. In other words, The law of supply states that there exists a positive relationship between the price and the quantity supplied of a good, implying that the supply curves normally slope upwards. As it is understood the correct answer is “A”. Market demand is the sum of all the quantities of a product demanded per period by all the buyers in the market. By market equilibrium, economists think of the price level at which demand and supply curves meet. At that price level the quantity demanded will be equal to the quantity supplied.  The quantities that the producers are willing and able to supply at every given prices are called quantity supplied. For a perfectly competitive firm, the curvature and the slope of the supply curve follow the marginal cost (MC) curve of the producers. By marginal cost, we mean the additional cost that the producers have to incur when they increase the production of a certain product by one unit. Marginal cost tends to increase as production increases. In other words, each additional unit produced will cost more to the firm to produce than the previous unit.