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': 'Area of the mitral valve in severe mitral stenosis during pregnancy \nSelect and explain. \nA. 4-6 cm2, B. 1-1.5 cm2, C. 1.5-2.5 cm2, D. 0.8-1 cm2', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Normal area of the mitral valve is 4-6cm2\nSevere mitral stenosis is less than 1.5cm2\nCritical area is less than 1cm2', 'role': 'assistant'}]