Ans. Option b). epithelial.
The lining of gastrointestinal tract, including stomach is made up of epithelial tissues. The tissue are composed of mucous columnar cells that produce mucus to protect stomach from enzymes and acids.
When acidity of stomach is increased due to bacterial infection, the acid present in gastric juice causes damage to the outer covering or epithelial layer of stomach.
Thus, the correct answer is option b). 'epithelial.'
