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': 'The definitive sign of pregnancy is : \nSelect and explain. \nA. HCG estimation, B. Quickening, C. Chadwick sign, D. Fetal skeleton in X-rays', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Fetal skeleton in X-rays', 'role': 'assistant'}]