This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
[{'content': 'Male-female differentiation of fetus occurs at \nSelect and explain. \nA. 2-4 weeks, B. 10-12 weeks, C. 16-18 weeks, D. 24-26 weeks', 'role': 'user'}, {'content': "Answer: B \nExplanation: Genotype of embryo is established at feilization. But male and female embryos are phenotypically distinguishbletill week 6. Ref: Gray's 39e/p-1289", 'role': 'assistant'}]