Where does the oxygen produced in respiration come from

When organisms are classified ,they are given a two part name

What are some of the immune functions of the lymphatic system? a. cleaning red blood cells from the blood and creating lymph fluids b. transporting lymph to the tissues and creating lymph fluids c. removing infectious agents and making white blood cells d. making red blood cells and removing infectious agents

Approximately how many times does an average human heart beat in a lifetime?