**Core Concept**
The stomach is a complex mucosal-lined organ containing various cell types that play crucial roles in digestion and absorption of nutrients. The main cell types in the stomach include parietal cells, chief cells, mucous neck cells, and enteroendocrine cells.

**Why the Correct Answer is Right**
The correct answer is **D. Pancreatic cells**. This is because pancreatic cells, also known as acinar cells, are primarily found in the pancreas, a separate organ involved in the production of digestive enzymes and hormones like insulin. These cells are not a part of the stomach lining, which is primarily composed of the aforementioned cell types. The stomach and pancreas work in concert to facilitate digestion, but they have distinct cellular compositions.

**Why Each Wrong Option is Incorrect**
* **Option A:** Parietal cells are found in the stomach and are responsible for secreting hydrochloric acid (HCl) and intrinsic factor, which plays a crucial role in vitamin B12 absorption.
* **Option B:** Chief cells, also known as peptic cells, are found in the stomach and secrete pepsinogen, the precursor to pepsin, a digestive enzyme that breaks down proteins.
* **Option C:** Mucous neck cells, also known as mucous cells, are found in the stomach and secrete mucus that protects the stomach lining from acid damage.

**Clinical Pearl / High-Yield Fact**
It's essential to remember the distinct cellular composition of the stomach and pancreas to understand their separate functions in digestion and nutrient absorption. This knowledge can be particularly useful when diagnosing and managing gastrointestinal disorders, such as peptic ulcers or pancreatic insufficiency.

**Correct Answer: D. Pancreatic cells**