**Core Concept**
Rumination disorder is a psychiatric condition characterized by the repeated regurgitation of food, which is then re-chewed, re-swallowed, or spat out. This behavior is not accompanied by the distress or concern about weight or body image seen in other eating disorders.

**Why the Correct Answer is Right**
Rumination disorder is distinct from other eating disorders in that it is primarily focused on the physical act of regurgitating and re-chewing food, rather than concerns about weight or body image. This behavior is often seen in infants and young children, but can also occur in adults. The exact cause of rumination disorder is unknown, but it is thought to be related to a combination of genetic, environmental, and psychological factors.

**Why Each Wrong Option is Incorrect**
**Option A:** Binge eating disorder is characterized by recurring episodes of eating large quantities of food in a short period, often accompanied by feelings of guilt or shame. While individuals with binge eating disorder may experience some regurgitation, it is not a primary feature of the disorder.
**Option C:** Bulimia nervosa is characterized by a cycle of binge eating followed by purging, which can include self-induced vomiting. While purging may involve regurgitation, it is not the same as the repeated, involuntary regurgitation seen in rumination disorder.
**Option D:** Anorexia nervosa is characterized by a distorted body image and an intense fear of gaining weight, leading to restrictive eating and significant weight loss. While individuals with anorexia nervosa may experience some regurgitation, it is not a primary feature of the disorder.

**Clinical Pearl / High-Yield Fact**
Rumination disorder is often associated with other psychiatric conditions, such as anxiety or depression, and may require a comprehensive treatment plan that addresses both the physical and emotional aspects of the disorder.

**✓ Correct Answer: B. Rumination disorder**