**Core Concept**
The question is testing the knowledge of specific antiemetics for chemotherapy-induced vomiting. Chemotherapy-induced vomiting is a common side effect of cancer treatment, and various antiemetic agents have been developed to manage this symptom. The question requires the student to identify the most specific antiemetic agent for this condition.

**Why the Correct Answer is Right**
The most specific antiemetic for chemotherapy-induced vomiting is **Ondansetron**. Ondansetron is a serotonin 5-HT3 receptor antagonist, which is the primary mechanism of action for preventing nausea and vomiting caused by chemotherapy. It works by blocking the action of serotonin on the 5-HT3 receptors in the chemoreceptor trigger zone (CTZ) of the brain, which is responsible for triggering vomiting. The 5-HT3 receptors are specifically involved in the emetic response to chemotherapy, making Ondansetron a highly effective and specific antiemetic agent for this indication.

**Why Each Wrong Option is Incorrect**
* **Option A:** Metoclopramide is a dopamine antagonist that is also used as an antiemetic, but it is not as specific for chemotherapy-induced vomiting as Ondansetron. Metoclopramide has a broader mechanism of action and can cause extrapyramidal side effects.
* **Option B:** Dexamethasone is a corticosteroid that is often used in combination with other antiemetic agents to prevent chemotherapy-induced vomiting, but it is not a specific antiemetic agent itself.
* **Option D:** Aprepitant is a substance P/neurokinin 1 (NK1) receptor antagonist that is used to prevent chemotherapy-induced nausea and vomiting, but it is not as specific as Ondansetron for this indication.

**Clinical Pearl / High-Yield Fact**
Ondansetron is a highly specific antiemetic agent for chemotherapy-induced vomiting due to its mechanism of action on the 5-HT3 receptors. It is often used in combination with other antiemetic agents to provide effective prophylaxis against chemotherapy-induced nausea and vomiting.

**Correct Answer:** C. Ondansetron