**Core Concept**
Zollinger Ellison syndrome is a clinical condition characterized by excessive gastric acid secretion, leading to severe peptic ulcers and diarrhea. It is caused by an overproduction of gastrin, a hormone that stimulates gastric acid secretion.

**Why the Correct Answer is Right**
The correct answer is related to gastrinomas, which are neuroendocrine tumors that secrete excessive amounts of gastrin. Gastrinomas are typically found in the duodenum or pancreas and can be sporadic or part of a multiple endocrine neoplasia syndrome (MEN-1). The overproduction of gastrin leads to hypergastrinemia, which in turn stimulates the parietal cells of the stomach to produce excessive amounts of gastric acid.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify the type of cell or tumor associated with Zollinger Ellison syndrome. While other types of tumors can cause excessive hormone production, gastrinomas are the specific type of tumor that leads to Zollinger Ellison syndrome.
* **Option B:** This option is incorrect because it does not accurately describe the clinical condition of Zollinger Ellison syndrome. While gastrinomas can cause severe peptic ulcers, the term "Zollinger Ellison syndrome" specifically refers to the excessive production of gastrin.
* **Option C:** This option is incorrect because it does not specify the type of tumor associated with Zollinger Ellison syndrome. While other types of tumors can cause excessive hormone production, gastrinomas are the specific type of tumor that leads to Zollinger Ellison syndrome.

**Clinical Pearl / High-Yield Fact**
Gastrinomas are often difficult to diagnose and may require a combination of imaging studies, endoscopic ultrasonography, and tumor markers to confirm the diagnosis. It is essential to consider Zollinger Ellison syndrome in patients with severe peptic ulcers or diarrhea, especially if they have a family history of multiple endocrine neoplasia syndrome.

**Correct Answer: C. Gastrinomas. Gastrinomas are neuroendocrine tumors that secrete excessive amounts of gastrin, leading to Zollinger Ellison syndrome.**