**Core Concept**
Dissociation hysteria, a form of dissociative disorder, involves a disconnection from one's thoughts, feelings, or experiences. This condition can manifest in various ways, including depersonalization, derealization, and amnesia.

**Why the Correct Answer is Right**
The most common form of dissociation hysteria is Dissociative Fugue, also known as Psychogenic Amnesia. In Dissociative Fugue, an individual suddenly forgets their past and assumes a new identity, often with a new name, occupation, and even a new family. This condition is characterized by a sudden and unexpected travel away from home or work, accompanied by an inability to recall one's past or previous identity. The exact mechanism is unclear, but it is thought to be related to a sudden and intense stressor that triggers a dissociative episode.

**Why Each Wrong Option is Incorrect**
**Option A:** Dissociative Amnesia is a condition where an individual forgets specific events or experiences, but not their past identity. It is not characterized by the sudden assumption of a new identity.
**Option B:** Depersonalization Disorder is a condition where an individual feels detached from their body or self, but still retains their sense of identity. It is not characterized by the sudden assumption of a new identity.
**Option C:** Dissociative Identity Disorder (DID), formerly known as Multiple Personality Disorder, is a condition where an individual has multiple distinct identities or personalities. While it is a form of dissociation, it is not the most common form of dissociation hysteria.

**Clinical Pearl / High-Yield Fact**
It's essential to differentiate between Dissociative Fugue and other forms of dissociation hysteria, as the treatment and management strategies differ. A thorough psychological evaluation and a detailed history are crucial in making an accurate diagnosis.

**Correct Answer: D. Dissociative Fugue**