Your Math Professor Has Assigned 20 Homework Problems That Are

Your math professor has assigned 20 homework problems that are due next week.After working for an hour,you notice you have completed 4 problems.After another hour,you have completed 3 more problems.During the third hour,you finish 2 problems.What economic principle best explains this?

A) The equilibrium principle: the supply of problems is greater than your demand for problems.
B) The increasing opportunity cost principle: you completed the easiest problems first.
C) The cost-benefit principle: the benefit of working an additional problem is less than the cost.
D) The principle of comparative advantage: you are better at English than at math.