Figure 5-6 Figure 5-6 Shows the Market for Measles

Figure 5-6 Figure 5-6 shows the market for measles vaccinations, a product whose use generates positive externalities.
-Refer to Figure 5-6. Why is there a deadweight loss?

A) because the marginal private benefit for each additional unit between Q₁ and Q₂ exceeds the marginal cost
B) because the marginal private cost for each additional unit between Q₁ and Q₂ exceeds the marginal private benefit
C) because the marginal social cost for each additional unit between Q₁ and Q₂ exceeds the marginal social benefit
D) because the marginal social benefit for each additional unit between Q₁ and Q₂ exceeds the marginal cost