Blood is the fuel that keeps you going! Oxygenated blood is brought to organs and tissues via the arteries, while veins bring deoxygenated blood back to the heart to be replenished. The point is, without the respiratory system your blood would be useless.
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.
The answer is D
Explanation:
I apologise for the late answer, but D would be the best one, as it does not discuss morality or anything differing from person to person. The effect it has on birds however, can be readily studied using the scientific method.
