John is trying to decide whether to go to college or to start working right out of high school. ...

John is trying to decide whether to go to college or to start working right out of high school. College as an investment is most likely justified when ________ is greater than the cost of going to college.
A) the present value of the difference between what John would earn as a college graduate and what he would earn as a high school graduate
B) the present value of what John would earn as a college graduate
C) the sum of lifetime earnings as a college graduate
D) the difference between the sum of lifetime earnings as a college graduate and the sum of lifetime earnings as a high school graduate