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
During which phase of the cell cycle is cellular content doubled? 
Select and explain. 
A. G2 phase, B. S phase, C. M phase, D. G1 phase
B: S phase
Answer: B: S phase 
Explanation: S phase - Synthetic phase, Doubling of nuclear content is the major role of this phase.