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: Social & Preventive Medicine
[{'content': 'Most common side effect of IUDs \nSelect and explain. \nA. Pain abdomen, B. Increased vaginal bleed, C. Abortion, D. Pelvic Infleammatiom', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Most common side effect : Increased vaginal bleed.\n2nd most common side effect : Pain.', 'role': 'assistant'}]