Which of the following best describes the short-run supply curve for an individual perfectly competitive firm?

A) It is the firm's marginal cost curve.
B) It is the upward-sloping part of the firm's marginal cost curve.
C) It is the vertical axis at prices less than minimum average variable cost and is the firm's marginal cost curve at prices above minimum average variable cost.
D) It is the vertical axis at prices less than minimum average total cost and is the firm's marginal cost curve at prices above minimum average total cost.

C