This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Etiological Factors of Neoplasia, Subject name: Pathology
[{'content': 'Arrange the cyclins and CDKs in cell cycle from G1 to S checkpoint. a) CDK6/ Cyclin E b) CDK4/ Cyclin D c) CDK 1 / Cyclin B d) CDK2/ Cyclin A \nSelect and explain. \nA. b,a,d,c, B. c,a,d,b, C. a,b,d,c, D. a,d,b,c', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Cyclins D, E, A, and B appear sequentially during the cell cycle and bind to one or more CDKs.', 'role': 'assistant'}]