Because Positive Externalities Present Benefits on Third Parties

Because positive externalities present benefits on third parties

A) private marginal benefits and social marginal benefits need to be considered to determine an optimal level of output.
B) social marginal benefits and social marginal costs need to be considered to determine an optimal level of output.
C) private marginal costs and private marginal benefits need to be considered to determine an optimal level of output.
D) social marginal costs and private marginal benefits need to be considered to determine an optimal level of output.