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
[{'content': 'In patient-controlled analgesia morphine is given commonly by \nSelect and explain. \nA. Intravenous, B. Intramuscular, C. Subcutaneous, D. Sublingual', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Patient-controlled analgesia (PCA) is now in widespread use for the management of breakthrough pain. With PCA, the patient controls a parenteral usually intravenous infusion device by pressing a button to deliver a preprogrammed dose of the desired opioid analgesic. Has better pain control using less opioid. REF: Katzung 13 TH ED. pg: 554', 'role': 'assistant'}]