Megan is 16 years old and overweight. She loves junk food and chocolate. A 10-minute walk to school is her only exercise every day. Which is the best method to help Megan lose weight?

A.only one meal a day and a 30-minute daily brisk walk

B.a low-fat diet and a game of tennis or a brisk walk every day

C.vitamin supplements and diet pills with a brisk daily walk

D.rigorous daily exercise with no change in her diet