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': 'Radioactivity acts on which phase of cell cycle: March 2010 \nSelect and explain. \nA. G1, B. G2, C. M, D. S', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B: G2 Most radiosensitive stage of cell cycle: G2M G2 G1 Most radioresistant phase: End of S phase', 'role': 'assistant'}]