Esther wants to work towards eating healthier. She is substituting fruit (like oranges, apples, and grapes) for her snacks during the day instead of chips and crackers. She is also trying to substitute veggies (carrots, peppers, and broccoli) while she studies in the evening instead of chocolate. Which strategy of change is Esther implementing?

a. Shaping Visualization
b. Countering Journaling
c. Habit stacking
d. Rewards