The answer is should be D because A includes food tracking, B includes your feelings which is really a diary, C you fitness log should not have picks of ur friends. So that leaves me with D.
The respiratory system works directly with the circulatory system to provide oxygen to the body. Oxygen taken in from the respiratory system moves into blood vessels that then circulate oxygen-rich blood to tissues and cells.
You will gain more health benefits because your training the muscles to be under stress.
