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': 'Most common skin manifestation of radiotherapy: \nSelect and explain. \nA. Erythema, B. Atopy, C. Hyperpigmentation, D. Dermatitis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. Erythema', 'role': 'assistant'}]