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: Radiology
Radioactivity acts on which phase of cell cycle: March 2010 
Select and explain. 
A. G1, B. G2, C. M, D. S
B: G2
Answer: B: G2 
Explanation: Ans. B: G2 Most radiosensitive stage of cell cycle: G2M G2 G1 Most radioresistant phase: End of S phase