This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oncology, Subject name: Surgery
Most radio resistant phase in cell cycle: 
Select and explain. 
A. G1, B. Early S, C. Late S, D. G2
C: Late S
Answer: C: Late S 
Explanation: Radiation energy is absorbed by tissue causing ionization or excitation, which are responsible for various biological effects. Susceptibility of various phases of cell cycle of radiation: G2M>M>G1> early S> late S phase Phase of cell cycle Comment G2M>G2 * Most sensitive to radiation End of S phase * Most resistant to radiation G1 * Radiation exposure leads to chromosomal aberration G2 * Radiation exposure leads to chromatid aberration