This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nuclear medicine, Subject name: Radiology
The "R"s of radiobiology include the following except: 
Select and explain. 
A. Repair, B. Reoxygenation, C. Repopulation, D. Reexcitation
D: Reexcitation
Answer: D: Reexcitation 
Explanation: Processes after radiation exposure are "4 R's" of radiobiology. Repair - Enzymatic mechanisms for healing intracellular injury. Reoxygenation- Process whereby oxygen is actually better distributed to ble cells following radiation injury and cell killing. Repopulation- Ability of the cell population to continue to divide and to replace dying and dead cells. Redistribution- Reflects the variability of a cell's radiosensitivity over the cell cycle.