The circulatory and respiratory systems work together to circulate blood and oxygen throughout the body. Air moves in and out of the lungs through the trachea, bronchi, and bronchioles. Blood moves in and out of the lungs through the pulmonary arteries and veins that connect to the heart.
Unrealistic means not realistic, or that it probably won't happen. If you set unrealistic goals, you will get discouraged and stop doing it because you probably won't be able to.
