Aerobic respiration refers to the use of oxygen by the body's cells to convert carbohydrates, amino acids and fats into energy while Anaerobic respiration releases energy by doing the same only it does so without oxygen.
Anaerobic respiration usually happens when the body is engaged in an activity that needs more oxygen than the lungs can supply.
These two energy sources usually work together to supply the body with enough energy however, the amount that each gives depends on the activity being done.
Both A and B, because if you have bad posture you will have weaker bones which can make you get hurt easier plus weaker bones will not be safe especially if you got in a car wreck.
