If Firms Enter a Purely Competitive Industry, Then in the Long

If firms enter a purely competitive industry, then in the long run this change will shift the industry

A) demand curve to the left, and the individual firm's demand curve will shift down.
B) demand curve to the right, and the individual firm's demand curve will shift up.
C) supply curve to the right, and the individual firm's demand curve will shift down.
D) supply curve to the left, and the individual firm's demand curve will shift up.