Federal Regulation Aimed at Reducing Greenhouse-Gas Emissions by Setting Some

Federal regulation aimed at reducing greenhouse-gas emissions by setting some maximum level of emissions from each firm

A) is the best approach because the costs of reducing emissions are different for each firm.
B) is the best approach because firms will quickly reduce air pollution.
C) will usually not produce the desired reduction in emissions at the lowest possible cost.
D) will achieve the largest but not the most efficient reduction in emissions.
E) will achieve the least reduction in emissions but be the most efficient.