Chemoreceptors sensitive to blood oxygen levels are primarily located in the

A) medulla oblongata.
B) carotid arteries.
C) right atrium.
D) left ventricle.
E) jugular veins.

Chemoreceptors sensitive to blood oxygen levels are primarily located in the carotid bodies, which are found at the bifurcation of the carotid arteries. These receptors detect changes in the oxygen content of the blood and send signals to the respiratory center in the brain to adjust breathing rates accordingly.