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 is cellular content doubled? \nSelect and explain. \nA. G2 phase, B. S phase, C. M phase, D. G1 phase', 'role': 'user'}, {'content': 'Answer: B \nExplanation: S phase - Synthetic phase, Doubling of nuclear content is the major role of this phase.', 'role': 'assistant'}]