Greg, a College Student, Knows That the Opportunity Cost of Taking

Greg, a college student, knows that the opportunity cost of taking a class this summer is $1,200.This means that:

A) Instead of taking the class, Greg could earn $1,200 by working instead.
B) Greg will need to pay $1,200 to take the class.
C) The difference between what he would earn working less the cost of the class is $1,200.
D) By taking the class, Greg will have the opportunity to earn $1,200 more in a job than he would without taking the class.