A. This is not the best answer. Programmed senescence results from genetic instructions to stop cell division, thus stopping hormonal changes or adequate performance by the immune system.
B. This is not the best answer. The free-radical theory explains that unstable atoms and molecules damage cells and that accumulated damage reduces cell function and causes late-onset disease.
C. This is not the best answer. The rate-of-living theory suggests that differences in metabolism influence rate of aging; rates of metabolism result from glucose intake.
D. This is not the best answer. The error-catastrophe theory explains that changes in cellular structure occur with each cell division.
E. This is the best answer. The cross-linking theory explains that cell function is compromised as proteins within the cell bond or link together during daily metabolic processes.