Answer: A.
Explanation:
Im pretty sure its A. Balance. All of them are important but balance is the main thing you'd need to know.
The digestive system helps process the food you have eaten in your body so then it can come out.
Eat Healthy food (avoid fatty, unhealthy foods)
Exercise, Mostly Cardio (Running, Walking, Jogging)
Limit meals to snacking 4-6 times a day, not eating huge portions all at once, like normal.
Do not over-eat, stay within your boundaries of how many calories your body needs per day
Stay positive: Having a positive attitude for all of the other steps is honestly a huge key, and staying committed to a plan that you have set.