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': 'Average pressure of uterine contractions during the first stage of labour is : \nSelect and explain. \nA. 100 mm Hg, B. 15 mm Hg, C. 20 mm Hg, D. 30 mm Hg', 'role': 'user'}, {'content': 'Answer: D \nExplanation: 30 mm Hg', 'role': 'assistant'}]