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': 'Which of the following step in cell cycle is known as restriction point? \nSelect and explain. \nA. G0 to G1, B. G1 to S, C. S to G2, D. G2 TO M', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Cells in G1 progress through the cycle and reach a critical stage at the G1/S transition, known as a restriction point, a rate limiting step for replication. Ref: Robbins 8th edition Chapter 3.', 'role': 'assistant'}]