Final answer:
The physical breakdown of food into smaller fragments when eating an apple is called mastication, which is the first step in the mechanical digestion process occurring in the mouth.
Step-by-step explanation:
When you eat an apple, the process by which it is physically broken down into smaller fragments is called mastication. This process is a part of mechanical digestion that starts in the mouth. During mastication, the teeth cut, grind and break the food into smaller pieces while saliva begins the chemical process of breaking the food down. This not only makes the food easier to swallow but also increases the surface area for enzymes to work on, making the digestion process more efficient. Ingestion is simply the act of taking food into the mouth, and mastication is a crucial step that follows. The correct answer to the question is c) Mastication.