Oncology student rounds:
Clinician: "Okay, what are the five front-line drugs for treating lymphoma?"
Students: "Cyclophosphamide, Doxorubicin, Vincristine, Prednisone, and L-asparaginase."
Clinician: "So if you were going to randomly not use one of those drugs, which one would you eliminate?"
Students: "Why?"
Clinician: "You're traveling to a desert island. You have 100 dogs with lymphoma, and you only have room for four drugs per dog. Which one do you leave behind?"
Students: "..."
(In case you were wondering, the answer is L-asparaginase)