Which of the Following Is Not True in a Long-Run $P = M C$

Multiple Choice

Which of the following is not true in a long-run perfectly competitive equilibrium?

A) $P = M C$ , where $P$ is market price and $M C$ is the marginal cost of a firm.
B) $P = A C$ , where $P$ is market price and $A C$ is the average cost of a firm.
C) $Q ^ { d } = n q$ , where $q$ is the supply of an individual firm, $n$ is the number of firms in the industry, and $Q ^ { d }$ is the market demand for a product.
D) Firms may earn negative profits.