Final answer:
Chewing food is primarily the mechanical breakdown of food into smaller pieces in the mouth, involving both mechanical digestion and ingestion. It does not involve propulsion, which refers to moving food through the alimentary canal, nor is it exclusive to chemical digestion which also begins in the mouth with the enzymes present in saliva.
Step-by-step explanation:
Chewing food is classified as mechanical breakdown. This process, which takes place in the mouth, involves physically breaking down food into smaller pieces without any chemical changes. It encompasses both mechanical digestion and ingestion, where the teeth and jaw work to mechanically chew the food, and the tongue helps to mix the food with saliva to form a bolus, facilitating swallowing.
Ingestion is the act of taking food into the body via the mouth, which also marks the beginning of the digestive process. During chewing, saliva starts the chemical digestion of carbohydrates, while propulsion aids in moving the food from the mouth to the esophagus.
Thus, all of the mentioned processes—a. ingestion, b. mechanical digestion, and c. chemical digestion—occurs in the mouth. However, the specific act of chewing is primarily considered mechanical digestion due to the physical nature of breaking down food. Furthermore, propulsion is a process that occurs throughout the alimentary canal, which is responsible for the movement of food along the digestive tract.