A Student Athlete Is Deciding Whether to Work Out for an Extra

A student athlete is deciding whether to work out for an extra hour. Her marginal benefit from another hour of exercise

A) depends on the cost of the workout.
B) is the benefit she gets from all the hours sheʹs worked out all week.
C) is less than the marginal cost of the additional hour.
D) is the benefit she receives from exercising the additional hour.