What is a characteristic of a perfectly competitive market?

a. Marginal revenue exceeds average revenue.

b. Average revenue exceeds total revenue.

c. Marginal revenue equals average revenue.

d. Average revenue exceeds marginal revenue.

also,

What is a short-run supply curve for a perfectly competitive firm?

a. the firm's average-variable-cost curve

b. the portion of the firm's average-total-cost curve that lies above the average-variable-cost curve

c. the portion of the firm's marginal-cost curve that lies above the average-variable-cost curve

d. the firm's marginal-revenue curve