A physiology student is tracing the digestion of a protein-rich meal through the stomach. Which statement best explains how the stomach carries out protein digestion while avoiding damage to its own tissues?

• A. Chief cells release pepsin, which neutralizes stomach acid while mucus dissolves food particles
• B. Parietal cells secrete hydrochloric acid that activates pepsinogen, while mucus-producing cells create a protective lining against acid
• C. Mucous cells secrete hydrochloric acid to digest proteins, while parietal cells release bicarbonate into the stomach lumen
• D. Smooth muscle contractions convert proteins directly into amino acids, while chief cells prevent erosion of the stomach wall