The horizontal sum of individual firms' MC curves (specifically the portions above AVC) is the:

A) short-run industry demand curve.
B) short-run industry supply curve.
C) long-run fixed cost curve.
D) long-run average variable cost curve.

Industry Supply Curve

A graphical representation showing the quantity of a good or service that producers are willing and able to supply at various prices.

Marginal Cost Curves

A graphical representation that shows how the marginal cost of producing an additional unit changes with the quantity produced.

AVC

Average Variable Cost, which is the variable cost per unit of output.