In the Short Run, the Best Policy for a Perfectly

In the short run, the best policy for a perfectly competitive firm is to

A) shut down its operation if price ever falls below average total cost.
B) produce and sell its product as long as price is greater than average variable cost.
C) shut down its operation if price falls between average total cost and average variable cost.
D) shut down its operation any time that marginal revenue is less than marginal cost.