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: Unknown
[{'content': 'The risk factors for placental abruption include the following except - \nSelect and explain. \nA. History of placental abruption in previous pregnancy, B. Hypertension, C. Diabetes mellitus, D. Preterm rupture of membranes', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans: C', 'role': 'assistant'}]