A cancer patient who is on cisplatin therapy develops severe vomiting on the 1st day of treatment,  drug indicated to treat this is:
Cisplatin induced vomiting has two phases.

EarlyPhase: It occurs within first 24 hours. 5 HT3 antagonists like ondansetron are the agents of choice for this condition. 
Delayed Phase: Vomiting occurring after 24 hours is less responsive to ondansetron and other drugs. It is best controlled by substance P antagonist like aprepitant
Aprepitant.
Ondansetron
Fosaprepitant.
All of the above.