The respiratory system works with the system to add oxygen to the blood and remove carbon dioxide from the body. what is it ? circulatory, muscular, digestive, or nervous ?

Circulatory.

Put simply, the circulatory system is the blood circulation (being moved around your body) system, so even if you didn't know exactly what happens you can tell it's circulatory because blood system must work with breathing system to remove CO2 from blood.

Ibelieve the answer is c.