Which of the following creates an incentive to increase the amount of an activity?
A.
an increase in the marginal cost of the activity and a decrease in the marginal benefit of the activity
B.
a decrease in the marginal cost of the activity and an increase in the marginal benefit of the activity
C.
constant marginal cost and constant marginal benefit of the activity
D.
None of the above create an incentive to increase the amount of an activity.