Under perfect competition, the short-run market supply curve is most accurately described by which of the following statements The market short-run supply curve is the:（）
A. average of the quantities at each price along the marginal cost curve for all firms in a given industry.
B. sum of the quantities at each price along the average total cost curve for all firms in a given industry.
C. sum of the quantities at each price along the marginal cost curves for all firms in a given industry.
