Assume That This Graph Illustrates a Perfectly Competitive Labor Market

Assume that this graph illustrates a perfectly competitive labor market. Suppose a minimum wage law required the wage to be at least $20 per hour in this market. If that happened, then:

A) there would be an excess supply of person-hours.
B) there would be excess demand for person-hours.
C) the demand for person-hours would shift to the right.
D) there would be no change the equilibrium number of person-hours.