**Core Concept**
Somatic passivity is a type of delusional disorder characterized by a false belief that one's bodily movements are being controlled by an external force, often with a malevolent intent. This phenomenon is a manifestation of the somatic passivity delusion, a symptom commonly associated with schizophrenia and other psychiatric disorders.

**Why the Correct Answer is Right**
The somatic passivity delusion arises from a disruption in the normal functioning of the brain's neural networks, particularly in the prefrontal cortex and the limbic system. This disruption leads to an abnormal interpretation of sensory information, resulting in the false belief that one's bodily movements are being controlled by an external force. The somatic passivity delusion is often accompanied by other psychotic symptoms, such as hallucinations and disorganized thinking.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because somatic passivity is not a feature of obsessive-compulsive disorder (OCD), which is characterized by recurring, intrusive thoughts and compulsions to perform specific rituals or behaviors.

**Option B:** This option is incorrect because somatic passivity is not a feature of post-traumatic stress disorder (PTSD), which is characterized by symptoms such as flashbacks, nightmares, and avoidance of triggers.

**Option C:** This option is incorrect because somatic passivity is not a feature of dissociative identity disorder (DID), which is characterized by the presence of two or more distinct identities or personalities.

**Clinical Pearl / High-Yield Fact**
The somatic passivity delusion is often accompanied by a sense of external control, which can manifest as a feeling of being manipulated or coerced by an external force. This can lead to a range of behaviors, including passivity phenomena, such as feeling one's body is being moved or manipulated by an external force.

**Correct Answer: A. Somatic passivity is a feature of schizophrenia.**