**Core Concept**
Cushing ulcers, also known as stress ulcers, are a type of mucosal defect that occurs in the stomach or duodenum in response to severe physiological stress, such as trauma, sepsis, or burn injuries. This phenomenon is characterized by the loss of gastric mucosal barrier function, leading to mucosal damage and ulceration.

**Why the Correct Answer is Right**
Cushing ulcers are caused by the imbalance between the protective and aggressive factors in the stomach mucosa. The protective factors include the production of mucus, bicarbonate, and prostaglandins, which maintain the integrity of the gastric mucosa. In contrast, the aggressive factors, such as gastric acid and pepsin, can cause mucosal damage. In response to severe physiological stress, the protective factors are decreased, and the aggressive factors are increased, leading to the development of Cushing ulcers.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Cushing ulcers are not caused by a single factor, such as Helicobacter pylori infection, but rather by a complex interplay between protective and aggressive factors in the stomach mucosa.
**Option B:** This option is incorrect because Cushing ulcers are not limited to the duodenum, but can also occur in the stomach.
**Option C:** This option is incorrect because Cushing ulcers are not typically associated with a specific type of ulcer, such as peptic ulcer disease.

**Clinical Pearl / High-Yield Fact**
Cushing ulcers are a common complication of severe physiological stress and can occur in any patient who has experienced significant trauma, sepsis, or burn injuries. Early recognition and treatment of Cushing ulcers are essential to prevent complications and improve patient outcomes.

**Correct Answer: C. Stress ulcers.**