Answer:
D. downsloping because successive units of a specific product yield less and less extra benefit.
Explanation:
This has to do with diminishing marginal productivity which causes that marginal costs to increase.
In true, close to 0 production, marginal costs decrease and marginal benefit curve increases. But because of diminishing marginal productivity, it (marginal costs curve) soons reaches a min and start increasing, which causes the marginal benefit curve to decrease