A Cap-And-Trade Policy Is an Efficient Method of Reducing Pollution

A cap-and-trade policy is an efficient method of reducing pollution because

A) all firms will be forced to reduce pollution.
B) only high-cost firms will be forced to reduce pollution.
C) only low-cost firms will be forced to reduce pollution.
D) those who can reduce pollution relatively more cheaply will have an incentive to buy permits.
E) those who can reduce pollution relatively more cheaply will have an incentive to sell permits.