A 55-year-old woman receiving cisplatin-based chemotherapy for ovarian cancer presents with nausea. She is started on a medication blocking substance P signaling at neurokinin-1 receptors for delayed emesis prevention. Her vital signs are stable (BP 128/82, HR 82, RR 16, Temp 37°C). Laboratory studies show normal electrolytes and creatinine 0.9 mg/dL. Upper endoscopy reveals no peptic ulceration. She denies prior antiemetic use. Which drug most likely has this mechanism of action?

1. A)Metoclopramide
2. B)Ondansetron
3. C)AprepitantGABARITO
4. D)Loperamide
5. E)Diphenhydramine