The Market for Watermelons in Adelaide Is Perfectly Competitive

The market for watermelons in Adelaide is perfectly competitive. A watermelon producer making zero economic profit could make an economic profit if the

A) average total cost of selling watermelons does not change.
B) marginal cost of selling watermelons rises.
C) average total cost of selling watermelons falls.
D) average total cost of selling watermelons rises.
E) marginal cost of selling watermelons does not change.