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: Surgery
[{'content': 'Most common cause of unilateral parotid swelling in a 27 yr old male is - \nSelect and explain. \nA. Warthins tumor, B. Pleomorphic adenoma, C. Adenocarcinoma, D. Haemangioma', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]