**Core Concept**
The treatment of **parkinsonism** involves managing its symptoms, primarily through **dopaminergic** therapy, which aims to increase **dopamine** levels in the brain. **Levodopa**, combined with **carbidopa**, is a cornerstone in this approach.

**Why the Correct Answer is Right**
**Levodopa**, in combination with **carbidopa**, is the most effective drug for the initial treatment of parkinsonism. **Carbidopa** inhibits the peripheral conversion of **levodopa** to **dopamine**, allowing more **levodopa** to cross the blood-brain barrier, thereby increasing its efficacy and reducing peripheral side effects.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because, although **anticholinergics** can be used for treating parkinsonism, they are not the first line of treatment.
**Option B:** Incorrect as **amantadine** is sometimes used for parkinsonism but is not the drug of choice for initial treatment.
**Option D:** Incorrect because **selegiline** is a **monoamine oxidase B (MAO-B)** inhibitor used as an adjunct in the treatment of parkinsonism.

**Clinical Pearl / High-Yield Fact**
Remember, **levodopa/carbidopa** is the gold standard for treating parkinsonism due to its ability to significantly improve symptoms by increasing **dopamine** availability in the brain.

**Correct Answer:** D. Levodopa/Carbidopa