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
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 
Select and explain. 
A. b,a,d,c, B. c,a,d,b, C. a,b,d,c, D. a,d,b,c
A: b,a,d,c
Answer: A: b,a,d,c 
Explanation: Cyclins D, E, A, and B appear sequentially during the cell cycle and bind to one or more CDKs.