The Figures Given Below Show the Demand (D)and Supply (S)

The figures given below show the demand (D) and supply (S) curves of labor in two different markets.Figure 16.3

-Why do skilled workers earn relatively higher wages than unskilled workers?

A) The marginal productivity of skilled workers is low.
B) The marginal cost of hiring skilled workers is low.
C) The supply of skilled workers is relatively less.
D) There is an abundant supply of skilled workers.
E) The marginal cost of hiring unskilled workers is high.