【单选题】Suppose that you are spending two hours a day studying economics, and your grade is 85 percent. You want a higher grade and decide to study for an extra hour a day. As a result, your grade rises to 90...
A.
5 point increase in your grade minus the opportunity cost to you of spending the hour studying.你的成绩增加5分,减去你花时间学习的机会成本。
B.
extra hour per day you spend on studying.每天花费额外的时间花在学习上。
C.
5 point increase in your grade.你的成绩提高5点。
D.
three hours per day you spend on studying.每天三个小时你花在学习上。