The correct answer is A. Cephalic phase
Step-by-step explanation:
In the digestive system and digestive process, there are different phases or stages. In the case of the cephalic phase, this is the first phase of the process and starts even before food enters in the organism, because fo this, the cephalic phase includes the anticipatory responses to food including salivation. This is the part or phase Pavlolv stimulated in his experiments because in this dogs salivated anticipating food and this was linked to the sound of a bell and that make dogs salivate even if there was no food.