A. This is not the best answer. Osteoporosis is typical over age 60, suggesting a common biological influence, but often begins in early adulthood as a result of poor nutrition and exercise habits.
B. This is not the best answer. Cardiovascular disease results from an increase in blood pressure and arteriosclerosis and clearly is influenced by both genetic predisposition and health habits.
C. This is not the best answer. The respiratory system is highly influenced by environmental factors such as pollutants and changes in other body systems such as the heart and skeletal systems.
D. This is not the best answer. Heightened autoimmunity results from decreases in T cells, but both internal and external stressors trigger the release of antibodies that destroy its own cells.
E. This is the best answer. Structural and functional changes in the brain and central nervous system occur throughout adulthood. The slowdown of the CNS affects physical and intellectual performance.