Refer to the Graph Shown, Which Shows the Demand and Supply

Refer to the graph shown, which shows the demand and supply for a new vaccine against the common cold. Suppose once vaccinated, a person cannot catch a cold or give a cold to someone else. As a result, the marginal social benefit curve will:

A) coincide with the market demand curve.
B) lie strictly below the market supply curve.
C) lie below the market demand curve.
D) lie above the market demand curve.