Friction, gravity, air resistance etc
Not too long but just enough so that your muscles can relax. I would say no less than 15 seconds but no more than 45 seconds
It's B because there are less mood elevating chemicals in people who aren't active. Which is why people with depression are told to try and be more active
Yes most schools has at least on dietitan so they can balance the food out.
If u drain blood from body the organs slowly stop there function and the person dies