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: Anatomy
[{'content': 'Blastocyst implantation close to internal os causes \nSelect and explain. \nA. Placenta pre, B. Placenta percreta, C. Placenta increta, D. Abruptio Placenta', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. Placenta pre- When the placenta is implanted paially or completely over the lower uterine segment, over and adjacent to the internal os, it is called placenta pre', 'role': 'assistant'}]