The Construction of the Economy's Marginal Social Benefit Curve for a Public

The construction of the economy's marginal social benefit curve for a public good reflects the fact that

A) all the individuals can consume the same unit of the good.
B) more than one supplier can provide the good.
C) the same unit of the good cannot be simultaneously shared by more than one person at a time.
D) the government can supply a public good at a lower cost than can a private supplier.