**Core Concept**
Hyperkinetic disorder is a psychiatric condition characterized by excessive motor activity, impulsivity, and inattention. It is also known as attention deficit hyperactivity disorder (ADHD). The disorder is associated with abnormalities in dopamine and norepinephrine neurotransmission in the brain.

**Why the Correct Answer is Right**
Hyperkinetic disorder is characterized by symptoms such as fidgeting, restlessness, and impulsivity. These symptoms are often accompanied by inattention and hyperactivity, which can interfere with daily functioning and relationships. The pathophysiology of hyperkinetic disorder involves impaired dopamine and norepinephrine signaling in the prefrontal cortex and basal ganglia, leading to abnormal motor control and cognitive processing.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because hyperkinetic disorder is indeed characterized by excessive motor activity.
**Option B:** This option is incorrect because hyperkinetic disorder is also associated with impulsivity and inattention.
**Option C:** This option is incorrect because hyperkinetic disorder is not typically characterized by a lack of motor activity, but rather an excess of it.

**Clinical Pearl / High-Yield Fact**
A key feature of hyperkinetic disorder is the presence of at least six symptoms of inattention and/or hyperactivity-impulsivity, which must be present in two or more settings (e.g., at home and in school). This distinction is crucial for diagnosis.

**Correct Answer:** D.