The correct option is D. Parietal cells are the epithelial cells which secrete hydrochloric acid and intrinsic factors. The cells are located in the gastric glands which are found in the linings of the walls of the stomach. The hydrochloric acid produced by the parietal cells helps in the conversion of the enzyme pepsinogen to pepsin during the digestion process.
Answer - C Snakes periodically shed their skin in order to regrow new skin. Birds migrating to the south and bears hibernating are also a result of normal periodic transitions. However, extinction of a type of shrimp is most likely a result of a drastic change in the environment.
