Answer:
d.
Explanation:
they were needed to reduce carbon monoxide in our environment to sustain fresher air, less pollution and wildlife..
Answer:
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:
Blood transports oxygen and nutrients to all the parts of the body so they can keep working. Blood carries carbon dioxide and other waste materials to the lungs, kidneys, and digestive system to be removed from the body. Blood also fights infections, and carries hormones around the body.
Explanation:
Urinary system. hope that helps