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: Gynaecology & Obstetrics
[{'content': 'Which of the following is not a sonographic criterion for cesarean scar pregnancy \nSelect and explain. \nA. Anterior uterine isthmic mass, B. Hourglass uterine shape, C. Empty cervical canal, D. Hyperechoic thin endometrial stripe', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Sonographic criteria for cesarean scar pregnancy include\xa0\n\nEmpty uterine cavity - bright hyperechoic endometrial stripe\nEmpty cervical canal\nIntrauterine mass seen in anterior part of uterine isthmus.', 'role': 'assistant'}]