Answer:
it takes the place of a noun
Explanation:
Probably the last one. It's the least realistic way to make your body healthy. If you are going to do exercise and make yourself healthy, friends would be helpful in that process and exercising is definitely a good way to be healthy.
The circulatory system is very useful. This system transports the food nutrients, and oxygen to the body cells. It also delivers of carbon dioxide and waste products. This helps the respiratory system by transporting nutrients to keep the lungs clean, and healthy.
The answer is C) Because nothing in this world is limited, especially not your nowledge base.