**Core Concept**
Peg cells are a type of mucous-secreting epithelial cell found in specific organs, particularly in the stomach. These cells are characterized by their short, stout shape and are involved in the production of mucin, a key component of mucus.

**Why the Correct Answer is Right**
Peg cells, also known as mucous neck cells, are a type of gastric epithelial cell that is specifically found in the stomach. They are responsible for producing mucin, which helps to protect the stomach lining from acid and pepsin. The production of mucin by peg cells is mediated by the enzyme MUC5AC, which is a key regulator of mucin synthesis. The presence of peg cells in the stomach is essential for maintaining the integrity of the gastric mucosa and preventing damage from acid and pepsin.

**Why Each Wrong Option is Incorrect**
**Option A:** Pancreas - While the pancreas does contain mucous-secreting cells, these cells are not referred to as peg cells and are not found in the same context as in the stomach.
**Option B:** Liver - The liver does not contain mucous-secreting cells of the type found in the stomach.
**Option C:** Duodenum - While the duodenum does contain mucous-secreting cells, these cells are not referred to as peg cells and are not found in the same context as in the stomach.

**Clinical Pearl / High-Yield Fact**
Peg cells are an important component of the stomach lining and play a crucial role in protecting the stomach from acid and pepsin. Damage to these cells can lead to gastric ulcers and other gastrointestinal disorders.

**Correct Answer:** C. Stomach.