Final answer:
Within the oral cavity, both mechanical and chemical digestion begin, involving mastication and enzymatic action in saliva.
Step-by-step explanation:
Within the oral cavity, both mechanical and chemical digestion begin. The correct answer to the student's question is C) digestion. In the mouth, food is initially processed through mastication, whereby the teeth and jaw break down food into smaller pieces in a mechanical manner. Concurrently, chemical digestion commences as enzymes in saliva begin the breakdown of complex molecules. These two processes work together to prepare food into a form that can be efficiently digested further as it moves through the gastrointestinal tract.