**Core Concept**
Parkinson's disease is a neurodegenerative disorder characterized by tremors, rigidity, bradykinesia (reduced mobility), and postural instability. The disease is primarily associated with the degeneration of dopaminergic neurons in the substantia nigra pars compacta, leading to a decrease in dopamine levels in the basal ganglia.

**Why the Correct Answer is Right**
The correct answer is based on the pathophysiology of Parkinson's disease. The degeneration of dopaminergic neurons results in a decrease in dopamine levels, which is responsible for the motor symptoms of the disease. Levodopa, a precursor to dopamine, is converted to dopamine in the brain, thereby increasing dopamine levels and alleviating symptoms. Dopamine agonists, such as pramipexole and ropinirole, directly stimulate dopamine receptors, mimicking the action of dopamine. MAO-B inhibitors, such as selegiline and rasagiline, prevent the breakdown of dopamine, increasing its availability in the brain.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not address the underlying pathophysiology of Parkinson's disease. While antipsychotics may be used to treat psychosis in Parkinson's disease, they are not the primary treatment for motor symptoms.

**Option B:** This option is incorrect as it does not directly address the motor symptoms of Parkinson's disease. While anticholinergics may be used to treat tremors, they are not the primary treatment for the disease.

**Option C:** This option is incorrect as it does not address the underlying pathophysiology of Parkinson's disease. While anticonvulsants may be used to treat tremors, they are not the primary treatment for the disease.

**Clinical Pearl / High-Yield Fact**
The Unified Parkinson's Disease Rating Scale (UPDRS) is a widely used assessment tool to evaluate the severity of Parkinson's disease. It assesses motor symptoms, including tremors, rigidity, and bradykinesia, as well as non-motor symptoms, such as mood and cognitive function.

**Correct Answer: D. Levodopa, dopamine agonists, or MAO-B inhibitors**