Markhira enjoys visiting her grandmother. Lately Markhira and her grandmother have been baking various desserts. Markhira's favo
rite is chocolate chip cookies. Every time they bake them, Markhira's stomach growls until she has a chance to eat one. After several weeks of visiting her grandmother and baking cookies, Markhira notices that her stomach growls every time she decides to go to her grandmother's house. The growling of Markhira's stomach at the thought of visiting her grandmother is caused by: