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: Pathology
[{'content': 'During which phase of the cell cycle, the cellular content of DNA is doubled? \nSelect and explain. \nA. Mitotic phase, B. G1 phase, C. G2 phase, D. S phase', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The cellular content of DNA is doubled during the S phase.', 'role': 'assistant'}]