This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anti-Neoplastic Agents, Subject name: Pharmacology
[{'content': 'Which of the following opioid is used by transdermal route in cases of malignancy associated pain - \nSelect and explain. \nA. Fentanyl, B. Morphine, C. Codeine, D. Oxycodone', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Fentanyl o Fentanyl is opioid analgesic used via transdermal delivery systems in case of chronic pain.", 'role': 'assistant'}]