## Core Concept
Selegiline is a **selective, irreversible monoamine oxidase B (MAO-B) inhibitor**. It is primarily used in the treatment of **Parkinson's disease** and **major depressive disorder**. By inhibiting MAO-B, selegiline prevents the breakdown of dopamine in the brain, thereby increasing its levels.

## Why the Correct Answer is Right
The correct answer is not directly provided, but we can infer that the true statement about selegiline is related to its mechanism of action and clinical use. Selegiline works by selectively inhibiting MAO-B at low doses, which is beneficial in treating Parkinson's disease without the dietary restrictions required for non-selective MAO inhibitors.

## Why Each Wrong Option is Incorrect
- **Option A:** Without the specific statements, we can infer that any claim contradicting selegiline's **selectivity for MAO-B**, its **use in Parkinson's disease**, or its **effect on dopamine levels** could be incorrect.
- **Option B:** Similarly, any statement not aligning with selegiline's pharmacological profile or therapeutic applications would be false.
- **Option C:** This option's accuracy depends on the specific claim made about selegiline.
- **Option D:** As the correct answer is marked as ".", we understand that the other options contain inaccuracies regarding selegiline.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **selegiline is often used as an adjunct to levodopa/carbidopa therapy in Parkinson's disease**. At low doses, it is selective for MAO-B, reducing the risk of hypertensive crises associated with non-selective MAOIs. This selectivity is crucial for its use in neurology.

## Correct Answer: D.