The correct answer is:
A. The respiratory system brings in oxygen into the body and the circulatory system carries the oxygen and blood around the body.
Here's a brief explanation: The respiratory system is responsible for inhaling oxygen from the environment and expelling carbon dioxide. Once oxygen is absorbed into the blood in the lungs, the circulatory system (specifically, the heart and blood vessels) transports that oxygen-rich blood to cells throughout the body, while also carrying carbon dioxide back to the lungs to be exhaled.