(C) Mucus and Pepsin
The gastric glands in the stomach wall release hydrochloric acid, pepsin (a protein-digesting enzyme), and mucus.
Source: Life Processes, section 5.2.4
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The passage clearly states: "These release hydrochloric acid, a protein digesting enzyme called pepsin, and mucus." Trypsin is secreted by the pancreas, not the stomach. Salivary amylase is released by the salivary glands. Mucus protects the stomach lining, and pepsin digests proteins — both come from gastric glands, making (C) correct.