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': 'Normal junctional Zone thickness of uterus is \nSelect and explain. \nA. 5 mm, B. 10 mm, C. 15 mm, D. 20 mm', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Junctional zone thickness is normally 5mm.', 'role': 'assistant'}]