The Optimal Level of Pollution Reduction Is That Level at Which

The optimal level of pollution reduction is that level at which

A) the total benefits of pollution reduction exceeds the total cost of pollution reduction by the largest amount.
B) the total benefits of pollution reduction equal the total cost of pollution reduction.
C) the marginal benefit of pollution reduction exceeds the marginal cost of pollution reduction by the largest amount.
D) the additional benefit of the last unit of pollution reduction equals the additional cost of the last unit of pollution reduction.
E) both a and d