Final answer:
Gastric pits are the openings at the end of tubular gastric glands in the gastric mucosa, which allow entry to each gastric gland for the secretion of gastric juice(option c).
Step-by-step explanation:
The openings at the end of tubular gastric glands in the gastric mucosa are known as gastric pits(option c).
These pits are narrow channels that are lined by the epithelial lining of the stomach mucosa.
They provide the entry point to each gastric gland, which in turn secretes gastric juice, a complex digestive fluid essential for the digestion process in the stomach.