The answer is 30-40% mortality reduction in all cause mortality. This is done when engaged in moderate intensity of physical activity such as walking, sports, stair climbing which is done in a regular basis for at least an hour. This tells that there are benefits even in achieving only moderate intensity of physical activities.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3034999/
Some cancers
immune deficits
bone and joint problems
specific anemia's
certain kinds of stroke
arthritis
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my answer wold be A. honest