**Core Concept**
Cerebellar disease can present with a variety of neurological signs and symptoms due to its role in motor coordination, balance, and proprioception. The cerebellum integrates sensory information from the vestibular system, proprioception, and vision to maintain posture and coordinate voluntary movements.

**Why the Correct Answer is Right**
The cerebellum is involved in the coordination and regulation of movements, including posture, gait, and fine motor tasks. Signs of cerebellar disease include ataxia, dysmetria, and nystagmus, which are all related to impaired motor coordination and balance. Cerebellar lesions can also cause dysarthria (speech disorders) and hypotonia (decreased muscle tone).

**Why Each Wrong Option is Incorrect**
**Option A:** Ataxia is a classic sign of cerebellar disease, characterized by a lack of coordination and balance.
**Option C:** Nystagmus, or involuntary eye movements, is also a common sign of cerebellar disease.

**Clinical Pearl / High-Yield Fact**
Remember the "Cerebellar Dysarthria" triad: ataxia, dysarthria, and nystagmus are all closely associated with cerebellar lesions.

**Correct Answer:** D.