In the Long Run, for a Perfectly Competitive Market, If

In the long run, for a perfectly competitive market, if economic profit is

A) less than zero, then some firms will exit the market and the market supply curve will shift leftward.
B) greater than zero, then some firms will enter the market and the market supply curve will shift rightward.
C) equal to zero, then there is no entry or exit of firms into or out of the market.
D) All of the above answers are correct.