This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
[{'content': 'Phenylbutazone use as an NSAID is restricted because : \nSelect and explain. \nA. It has lower anti-inflammatory efficacy than other NSAIDs, B. It has potential to cause agranulocytosis, C. It has weak analgesic action, D. It alters the protein binding and metabolism of many drugs', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]