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': "According to Hellin's law chances of twins in pregnancy are: \nSelect and explain. \nA. 1 in 60, B. 1 in 70, C. 1 in 80, D. 1 in 90", 'role': 'user'}, {'content': 'Answer: C \nExplanation: According to Hellin’s rule\nThe mathematical frequency of multiple pregnancy is:\n\nTwins 1 in 80\nTriplets 1 in (80)2\nQuadruplets 1 in (80)3 and so on', 'role': 'assistant'}]