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.
Answer: Blue because of google lol
Answer: By breathing out
Explanation: Breathing in oxygen and breathing out CO2.
(Cows also release CO2 by farting)
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