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': 'Mature graffian follicle preovulatory is less than \nSelect and explain. \nA. 12mm, B. 1.4mm, C. 18 mm, D. 25mm', 'role': 'user'}, {'content': 'Answer: C \nExplanation: 18 mm', 'role': 'assistant'}]