Which segment of the cost curves represents the supply curve for a perfectly competitive firm in the long run?

Explanation

In the long run, a competitive firm's supply curve corresponds to the portion of the marginal cost curve that lies above the average total cost curve. This is because the firm will only supply output if the price covers all costs, including both variable and fixed costs, which is represented by the average total cost. Other curves or portions do not accurately reflect the firm's supply decisions in the long run.