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: Medicine
[{'content': 'Percentage of offspring affected by colour blindness when a healthy male and heterozygous female marry \nSelect and explain. \nA. 0, B. 25%, C. 50%, D. 100%', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]