The Following Questions Refer to the Graph Below

The Following Questions Refer to the graph below.
-The slope of the supply curve indicates that the

A) Marginal cost of a year of education is constant
B) Marginal benefit of an additional year of education increases.
C) Marginal benefit of an additional year of education is constant
D) Marginal benefit of an additional year of education increases
E) Cost of education is subsidized by the public