The above figure shows the marginal social benefit and marginal social cost curves of coffee in the nation of Kaffenia. When marginal social benefit is equal to the marginal social cost of coffee in Kaffenia,
选项：

A:three hundred pounds per day will be produced and consumed.
B: the efficient quantity of coffee is being produced and consumed.
C: any decrease in coffee consumption or production would result in a deadweight loss.
D: All of the above are correct.