This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Central Nervous system, Subject name: Pharmacology
Drug of choice for controlling severe pain in cancer patient is: 
Select and explain. 
A. Morphine, B. Diclofenac, C. Ibuprofen, D. Codiene
A: Morphine
Answer: A: Morphine 
Explanation: Ref: Katzung 10/e p449 Opioids like morphine can be used to treat severe pain associated with terminal cancers.