<span>A. Mammals use a closed, double-loop circulatory system aided by a four-chambered hearts.
The four chambered heart of a mammal is divided into two atria and two ventricles. Double-loop circulatory system is used. One loop for oxygenated blood, the other loop for deoxygenated blood.</span>
It does not exist. Ca is 2+ and SiO4 is 4-, so it would in that case be Ca2SiO4, which does not exist either.
Answer:
to the lungs
Explanation:
it needs to be reoxygenated so it goes back into the lungs