**Core Concept**
Zollinger-Ellison syndrome is a rare disorder characterized by excessive gastric acid production due to high levels of gastrin, a hormone that stimulates the parietal cells in the stomach to secrete gastric acid. This leads to severe peptic ulcers and diarrhea.

**Why the Correct Answer is Right**
The syndrome is caused by a gastrin-secreting tumor, usually a gastrinoma, which can be found in the pancreas or the duodenum. The high levels of gastrin stimulate the parietal cells in the stomach to secrete excessive amounts of gastric acid, leading to peptic ulcers and diarrhea. The increased acid production can also lead to complications such as perforation and bleeding.

**Why Each Wrong Option is Incorrect**
**Option A:** Excessive gastric acid production is a hallmark of the syndrome, so this option is incorrect.
**Option B:** Diarrhea is a common symptom of Zollinger-Ellison syndrome due to the high levels of gastric acid in the small intestine, which can lead to malabsorption of nutrients.
**Option C:** Peptic ulcers are a common complication of Zollinger-Ellison syndrome, so this option is incorrect.

**Clinical Pearl / High-Yield Fact**
The "rule of 30s" can be remembered for Zollinger-Ellison syndrome: 30-50% of patients have a family history, 30-50% have a duodenal ulcer, and 30-50% have a gastrinoma located in the duodenum.

**Correct Answer:** C. Peptic ulcers are a common complication of Zollinger-Ellison syndrome.