Answer:
Gastric epithelium.
Step-by-step explanation:
Peptic ulcers are defined as sores in inner lining of stomach due to break in gastric epithelium. Bacterial infections are major causative agents for peptic ulcers.
Our stomach is protected from gastric acid by the cells of epithelial lining (mucosa) that produces bicarbonate ions, which can neutralize gastric acid.
Some bacteria increase production of acid, which damage tissues of epithelial lining. It leads to inflammation of stomach lining and cause peptic ulcers.
Thus, the correct answer is 'gastric epithelium.'