**Core Concept**
The question is testing the student's knowledge of anthelmintic therapy, specifically the treatment of roundworm (Toxocara cati or Ascaris lumbricoides) infections. The correct treatment involves using an anthelmintic agent that targets the worm's nervous system, causing paralysis and eventual expulsion from the host.

**Why the Correct Answer is Right**
Pyrantel is a type of anthelmintic medication that works by stimulating the nicotinic acetylcholine receptors in the worm's nervous system, causing muscle contraction and paralysis. This leads to the worm's expulsion from the host through the gastrointestinal tract. Pyrantel is effective against a wide range of nematodes, including roundworms.

**Why Each Wrong Option is Incorrect**
**Option A:** Albendazole is a benzimidazole anthelmintic that works by inhibiting microtubule polymerization in the worm's cells, ultimately leading to cell death. While it is effective against many types of nematodes, it is not the first-line treatment for roundworm infections.
**Option B:** Ivermectin is a macrocyclic lactone anthelmintic that works by binding to glutamate-gated chloride channels in the worm's nervous system, causing hyperpolarization and paralysis. It is effective against many types of nematodes, but its use is often reserved for more severe or complicated infections.
**Option C:** Metronidazole is an antibiotic that works by inhibiting DNA synthesis in bacteria and protozoa. It is not effective against nematodes and is not used to treat roundworm infections.

**Clinical Pearl / High-Yield Fact**
When treating roundworm infections, it's essential to note that pyrantel is often used in combination with other anthelmintics, such as albendazole, to ensure complete clearance of the infection.

**Correct Answer:** C. Pyrantel.