Suppose That a Firm That Produces Widgets Employs Welders as the Labor

Suppose that a firm that produces widgets employs welders as the labor input for production.The demand for welders is:

A) derived from the total industry output of widgets.
B) represented by the marginal value product curve if the firm is monopolist in the output market.
C) derived from the demand curve for widgets faced by the firm.
D) represented by the marginal revenue product curve if the firm is competitive.