For a Monopsony, the Marginal Cost of Labor Curve Lies

For a monopsony, the marginal cost of labor curve lies above the labor supply curve because

A) to hire one more unit of labor requires that the wage be raised for all units of labor.
B) to hire one more unit of labor requires that the wage be raised for just the last unit of labor hired.
C) to hire one more unit of labor, the firm uses its monopsony power to not raise the wage it pays.
D) to hire one more unit of labor requires that the firm offer a lower wage.