This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General Concepts, Subject name: Pathology
[{'content': 'Transition from G2 to M phase of the cell cycle is controlled by which of the following cyclins? \nSelect and explain. \nA. Cyclin D, B. Cyclin A, C. Cyclin E, D. Cyclin B', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Examples of cyclin/CDK complexes controlling the cell cycle. Cyclin B/CDK1 Regulates the transition from G2 to M phase Cyclin D-Cdk4/6 Regulates the transition from G1-S Cyclin D/CDK4, Cyclin D/CDK6, Cyclin E/CDK2, Cyclin A/CDK2 and cyclin B/ CDK1 Active in S phase', 'role': 'assistant'}]