Question

What system does the circulatory system work with to obtain oxygen for the body?

Answer 1

Respiratory system, because the lungs and diaphragm would get the oxygen from the air, and transfer them to the circulatory system (that's a pretty basic explanation, there's much more to it)

Answer 2

Respiratory system , absorbs oxygen from the air and  mixes it with the blood and pumped back to the heart