If a person takes an action if, and only if, the extra benefits from taking that action exceed the extra costs, then that person is:

If a person takes an action if, and only if, the extra benefits from taking that action exceed the extra costs, then that person is:
A.not rational.
B.following the Cost-Benefit Principle.
C.following the Scarcity Principle.
D.not following the Cost-Benefit Principle.
正确答案：following the Cost-Benefit Principle.