**Core Concept**
Curling's ulcer is a type of **acute peptic ulcer** that occurs in the setting of severe burns, resulting from the combination of physiological stress and mucosal ischemia. The pathogenesis involves the release of **stress hormones** such as gastrin and histamine, leading to increased gastric acid production.

**Why the Correct Answer is Right**
The most common site for Curling's ulcer is the **duodenum**, which is the first part of the small intestine. This is because the duodenum is particularly susceptible to the damaging effects of excess gastric acid and pepsin, especially in the context of compromised mucosal defense mechanisms following severe burns.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because, while the stomach can be a site for peptic ulcers, it is not the most common location for Curling's ulcer.
**Option B:** Incorrect as the esophagus is less commonly involved in peptic ulcer disease related to burns.
**Option C:** Incorrect because, although the jejunum can be affected by various types of ulcers, it is not the typical site for Curling's ulcer.

**Clinical Pearl / High-Yield Fact**
It's crucial to remember that Curling's ulcer is distinct from Cushing's ulcer, which occurs in the setting of brain injury. Both are stress-related ulcers but have different typical locations and pathophysiologies.

**Correct Answer:** D. Duodenum