Answer:
Option C. because of the law of diminishing returns.
Step-by-step explanation:
The law of diminishing returns states that as more of any particular input is added, while holding all the other inputs constant, its marginal product will eventually decline. Therefore, as marginal productivity declines, so does marginal revenue.
In the scenario presented above, the marginal productivity of each successive addition of labor, will eventually lead to an increase which is less than proportionate.