Answer:
D. The marginal benefit from reducing another ton of pollution should be equal to the marginal cost.
Step-by-step explanation:
The benefit arises when the cost is fully recovered, as in the given case the marginal cost for each ton reducing the pollution shall be equal to the benefit of marginal ton of pollution reduced.
Whenever, marginal cost is less than the benefit it is favorable but it is not permanent and thus, not valid, in case the cost is equal to the befit it is at break-even and is beneficial in every situation for the economy and environment.