Under the EPA's "Bubble Concept

Under the EPA's "bubble concept":

A) factories that keep their air pollution under established limits may receive "pollution credits," which they can sell.
B) individual factories in the bubble may exceed emission levels of air pollution as long as all the factories in the bubble do not exceed acceptable levels.
C) both water and air pollution are governed by its provisions.
D) two of the above.(a and b)
E) none of the above.