**Core Concept**
Drug-induced parkinsonism is a condition characterized by parkinsonian symptoms that develop as a side effect of certain medications, particularly antipsychotics and antiemetics. The pathophysiology involves blockade of dopamine receptors in the nigrostriatal pathway, leading to decreased dopamine activity.

**Why the Correct Answer is Right**
The drug of choice in drug-induced parkinsonism is an anticholinergic agent, which helps to alleviate symptoms by increasing the availability of dopamine in the synaptic cleft. The correct option is an anticholinergic agent, specifically trihexyphenidyl, which is a muscarinic receptor antagonist. This class of drugs can effectively counteract the effects of dopamine receptor blockade and improve parkinsonian symptoms.

**Why Each Wrong Option is Incorrect**
**Option A:** Dopamine agonists, such as pramipexole, may be used in Parkinson's disease but are not the first-line treatment for drug-induced parkinsonism.
**Option B:** Amantadine is an NMDA receptor antagonist with some dopaminergic effects, but it is not the preferred treatment for drug-induced parkinsonism.
**Option C:** This option is blank, so I will skip to the next one.

**Clinical Pearl / High-Yield Fact**
It's essential to note that drug-induced parkinsonism can be reversible by discontinuing the offending medication, making it crucial to consider medication history when evaluating patients with parkinsonian symptoms.

**Correct Answer: C. Trihexyphenidyl**