In the Short Run in a Perfectly Competitive Industry

In the short run in a perfectly competitive industry,

A) each firm's supply curve is horizontal,but the market supply curve is upward sloping
B) the marginal cost curve equals the marginal revenue curve
C) the market supply curve is upward sloping because each firm's supply curve is upward sloping
D) the market demand curve is the sum of each consumer's marginal revenue curve
E) each firm earns only a normal profit