How Would a Tax on Carbon Emissions Increase Economic Efficiency

How would a tax on carbon emissions increase economic efficiency?

A) Reduce emissions to the level where the lowest marginal benefit equals the marginal social cost.
B) Reduce emissions to the level where the highest marginal benefit equals the marginal social cost.
C) Reduce emissions to the level where the average marginal benefit equals the marginal social cost.
D) Reduce emissions to the level where all marginal benefits equal the marginal social cost.