because as you rise the pressure increases and the air gets compressed making the oxygen to decrease and go down
"the liver produces bile which emulsifies fats i.e. breaks them down into small droplets for a larger surface area. this will increase the rate at which the fat is digested by lipase. bile also neutralizes the acid produced by the stomach to provide ideal alkaline conditions for enzymes in the small intestine."
if scientists want to solve an environmental problem, they are most likely to