**Core Concept:** Akathisia is a side effect of antipsychotic medications, characterized by restlessness, inner unease, and an irresistible urge to move. It is caused by the blockade of dopamine D2 receptors in the extrapyramidal system.

**Why the Correct Answer is Right:** Akathisia is a common side effect of antipsychotic drugs, particularly the typical antipsychotics (e.g., chlorpromazine, haloperidol). The correct answer, **D. Restlessness**, is a manifestation of akathisia as it is a consequence of the blockade of dopamine D2 receptors in the extrapyramidal system, which leads to increased dopamine activity and resulting in restlessness.

**Why Each Wrong Option is Incorrect:**

A. **Restlessness (Option A)**: Restlessness is a manifestation of akathisia, but akathisia is a broader term that includes restlessness, inner unease, and an irresistible urge to move.

B. **Inner Unease (Option B)**: Inner unease is one of the manifestations of akathisia, along with restlessness and the irresistible urge to move.

C. **Irresistible Unease (Option C)**: This option is inaccurate, as akathisia manifests as an irresistible urge to move, not unease.

D. **Restlessness (Correct Answer)**: Restlessness is a manifestation of akathisia due to dopamine D2 receptor blockade.

**Clinical Pearl:** Akathisia can be severe in some cases, leading to suicidal ideation. Early recognition and management can prevent complications.

**Correct Answer:** D. Restlessness