The Optimal Amount of Pollution Abatement Is Generally Less Than

The optimal amount of pollution abatement is generally less than 100 percent. Complete (100 percent ) abatement would be optimal if

A) the marginal cost of abatement is always zero.
B) the marginal cost of abatement exceeds the marginal benefit of abatement at all levels of abatement.
C) the marginal benefit of abatement is zero.
D) the marginal cost of abatement is positive but less than the marginal benefit of abatement.
E) none of the above -- we cannot even imagine a situation in which complete abatement would be optimal.