**Core Concept**
Intrinsic factor is a glycoprotein produced in the stomach that plays a crucial role in vitamin B12 absorption. It binds to vitamin B12 in food and facilitates its absorption in the ileum of the small intestine. The intrinsic factor is secreted by specific cells in the gastric glands.

**Why the Correct Answer is Right**
The intrinsic factor is secreted by the parietal cells in the gastric glands. Parietal cells are also known as oxyntic cells and are responsible for secreting hydrochloric acid (HCl) and intrinsic factor. The intrinsic factor is produced in the canaliculi of the parietal cells and is secreted into the gastric lumen, where it binds to vitamin B12. The enzyme pepsinogen is also secreted by chief cells in the gastric glands and is converted to pepsin, which helps to break down proteins in the stomach.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the chief cells in the gastric glands produce pepsinogen, not intrinsic factor.
**Option B:** This option is incorrect because the mucous neck cells in the gastric glands produce mucin, which forms a protective layer on the surface of the stomach.
**Option C:** This option is incorrect because the enterochromaffin-like (ECL) cells in the gastric glands produce histamine, which stimulates the release of HCl from the parietal cells.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that vitamin B12 deficiency can lead to megaloblastic anemia, which is characterized by large red blood cells. Intrinsic factor deficiency, also known as pernicious anemia, is a common cause of vitamin B12 deficiency.

**Correct Answer: C. Parietal cells**