Suppose that when you study 4 hours for an exam, your mark is 80 percent. If you study for an extra hour, your mark is 85 percent. Choose the correct statement. O A. The marginal increase from studying one more hour is 15 percent. O B. The marginal cost of studying one more hour is 85 percent. O C. The marginal benefit from studying one more hour is 5 percent. O D. The marginal benefit from studying one more hour is 80 percent