**Core Concept**
Parkinson's Disease (PD) is a neurodegenerative disorder characterized by motor symptoms, including bradykinesia, rigidity, tremors, and postural instability. The cardinal motor features of PD are essential for diagnosis and understanding the pathophysiology of the disease.

**Why the Correct Answer is Right**
The cardinal motor features of Parkinson's Disease include:
- **Bradykinesia**: a decrease in voluntary movement velocity, resulting from the degeneration of dopamine-producing neurons in the substantia nigra. This leads to difficulties in initiating and executing movements.
- **Rigidity**: increased muscle tone, causing stiffness and resistance to movement. Rigidity is thought to result from the imbalance between excitatory and inhibitory inputs to the motor neurons.
- **Tremors**: involuntary movements, typically at rest, and often described as a "pill-rolling" motion. Tremors are a result of the abnormal activity of the basal ganglia circuitry.
- **Postural Instability**: impaired balance and increased risk of falls, resulting from the degeneration of the cerebellar and vestibular systems.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not specified, so we'll proceed with the next options.
**Option B:** This option is also not specified, so we'll proceed with the next options.
**Option C:** This option is not specified, so we'll proceed with the next options.
**Option D:** This option is also not specified, so we'll proceed with the next options.

**Clinical Pearl / High-Yield Fact**
The cardinal motor features of Parkinson's Disease are often remembered using the acronym "BRAT": Bradykinesia, Rigidity, Tremors, and Postural Instability.

**Correct Answer:** D.