**Core Concept**
Trichobezoar is a type of gastrointestinal foreign body, consisting of a mass of swallowed hair that accumulates in the stomach and intestines, often leading to intestinal obstruction or other complications. This condition is also known as "raper's hair ball."

**Why the Correct Answer is Right**
The most common presentation of trichobezoar is abdominal pain, often accompanied by nausea, vomiting, and weight loss. This is due to the mechanical obstruction caused by the bezoar, which can lead to bowel ischemia, perforation, or even death if left untreated. The condition is more common in individuals with psychiatric disorders, such as trichotillomania (excessive hair pulling), or in those with poor oral hygiene or eating habits.

**Why Each Wrong Option is Incorrect**
* **Option A:** While abdominal distension can be a symptom of trichobezoar, it is not the most common presentation.
* **Option B:** Diarrhea is not typically associated with trichobezoar, as the condition is more likely to cause intestinal obstruction.
* **Option C:** Fever is not a characteristic symptom of trichobezoar, although it may occur in cases of secondary infection or bowel perforation.

**Clinical Pearl / High-Yield Fact**
Trichobezoar is often associated with trichotillomania, a psychiatric disorder characterized by excessive hair pulling. A high index of suspicion is necessary in patients with a history of psychiatric disorders or unexplained gastrointestinal symptoms.

**Correct Answer: D. Abdominal pain**