The Figure Below Shows the Supply Curve for Labor

The figure below shows the supply curve for labor.Figure 16.1

-Why does the labor market have more than one equilibrium wage rate?

A) Workers differ in their productivities.
B) Productivity of workers increases initially but later declines.
C) The labor demand curve is backward bending.
D) Marginal revenue product of different inputs used by firms vary.
E) Employers compete among themselves to hire the best workers.