A．To justify the study of the Boston University Medical Center.
B．To stress the importance of maintaining proper weight.
C．To support the statement made by York Onnen.
D．To show the most effective way to lose weight.

A．Controlling one's calorie intake is more important than doing exercise.
B．Even occasional exercise can help reduce weight.
C．Weight reduction is impossible without exercise.
D．One could lose ten pounds in a year's time if there's no increase in food intake.