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
Transition from G2 to M phase of the cell cycle is controlled by which of the following cyclins? 
Select and explain. 
A. Cyclin D, B. Cyclin A, C. Cyclin E, D. Cyclin B
D: Cyclin B
Answer: D: Cyclin B 
Explanation: 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