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: Radiology
[{'content': 'On 4 Gy dose on the scalp, alopecia develops within: \nSelect and explain. \nA. 3-4 wk, B. 6-8 wk, C. 10-12 wk, D. 14-16 wk', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]