A Long-Run Supply Curve Is Flatter Than a Short-Run Supply

Multiple Choice

A long-run supply curve is flatter than a short-run supply curve because

A) firms can enter and exit a market more easily in the long run than in the short run.
B) long-run supply curves are sometimes downward sloping.
C) competitive firms have more control over demand in the long run.
D) firms in a competitive market face identical cost structures.