The competitive firm's short-run supply curve
A.
a. is its marginal revenue curve, but only the portion where marginal revenue exceeds marginal cost.
B.
b. is its marginal cost curve.
C.
c. is its marginal cost curve, but only the portion above the minimum of average total cost.
D.
d. is its marginal cost curve, but only the portion above the minimum of average variable cost.