**Core Concept**
Intrinsic factor is a glycoprotein essential for vitamin B12 absorption in the small intestine. It is produced in the gastric glands and binds to vitamin B12 in the stomach, facilitating its transport to the ileum via the ileal mucosa.

**Why the Correct Answer is Right**
Parietal cells, located in the gastric glands of the stomach, secrete intrinsic factor as part of their normal function. This factor binds to vitamin B12 in the gastric lumen, forming a complex that is absorbed in the terminal ileum. Without intrinsic factor, vitamin B12 cannot be absorbed, leading to pernicious anemia. Parietal cells are also responsible for secreting hydrochloric acid and gastrin-releasing peptide, but intrinsic factor is their specific product.

**Why Each Wrong Option is Incorrect**
Option A: Chief cells secrete pepsinogen and gastric proteases, not intrinsic factor.
Option C: Enterochromaffin cells are involved in regulating gut motility and releasing serotonin, not intrinsic factor.
Option D: B cells in the gastric glands produce immunoglobulins and are not associated with intrinsic factor secretion.

**Clinical Pearl / High-Yield Fact**
Intrinsic factor is secreted exclusively by parietal cells, and its deficiency leads to pernicious anemia due to impaired vitamin B12 absorption. This condition is often associated with autoimmune destruction of parietal cells in the gastric mucosa.

✓ Correct Answer: B. Parietal cells