When Electricity Buyers and Electric Utility Companies Trade with One

When electricity buyers and electric utility companies trade with one another,the electric utilities may generate electricity with a coal-burning power plant.This produces sulfur dioxide,nitrogen dioxide,particulates,and other air pollutants,which affect people who may not be among the buyers or sellers.This phenomenon is known as

A) a negative externality.
B) excess supply.
C) resource overuse.
D) mitigation.