Because it's apart of their History.
Oxidative stress is an imbalance between the production of free radicals (highly unstable molecules that are naturally formed when you exercise and when your body converts food into energy) and the ability of the body to counteract or detoxify their harmful effects through neutralization by antioxidants. Antioxidants such as thiols or ascorbic acid prevent free radicals forming due to oxidation. Some ways our bodies can be exposed to oxidative stress are by having an unbalanced diet, smoking, or sun exposure. Some ways to prevent oxidative stress are having a healthy diet, not smoking, exercising regularly and wearing sunscreen.
A warm soft place to sleep and a quiet environment. Maybe certain music can be a factor too.
A and B probably take the longest
A standard unit of measurement based on the distance to the sun is the astronomical unit.
