You notice that when a new yoga class is offered at the student recreation center at a highly desirable time, some students from the other yoga classes go to the new class instead. Which economic principle does this statement BEST represent? Question 6 options: A) Choices are necessary because resources are scarce. B) The true cost of something is its opportunity cost. C) People usually respond to incentives, exploiting opportunities to make themselves better off. D) "How Much" is a decision a the margin