**Core Concept**
Toxocariasis, caused by the roundworm *Toxocara*, is a zoonotic infection that can affect humans, particularly children. The infection is usually acquired through fecal-oral transmission or by ingesting contaminated soil or food.

**Why the Correct Answer is Right**
The treatment of choice for toxocariasis involves antiparasitic medications that target the worm's lifecycle. **Praziquantel** is a broad-spectrum anthelmintic that works by binding to the nicotinic acetylcholine receptors on the muscle cells of the parasite, causing muscle contractions and paralysis, ultimately leading to the expulsion of the worm from the host. This mechanism is specific to the parasite's muscle physiology, making **praziquantel** an effective treatment for roundworm infections.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because **metronidazole** is an antibiotic used to treat bacterial infections, particularly those caused by anaerobic bacteria. It is not effective against roundworms.
* **Option B:** This option is incorrect because **ivermectin** is an antiparasitic medication, but it is primarily used to treat infections caused by nematodes, such as filarial worms and strongyloides. While it may have some activity against roundworms, it is not the first-line treatment.
* **Option C:** This option is incorrect because **antibiotics** are not effective against roundworms, which are parasitic worms.

**Clinical Pearl / High-Yield Fact**
In cases of suspected toxocariasis, a complete history and physical examination are crucial in diagnosing the infection. Patients may present with symptoms such as cough, asthma, or ocular lesions, making a thorough clinical evaluation essential for diagnosis and treatment.

**Correct Answer:** C. Ivermectin