Answer: Red blood cell
Step-by-step explanation:
RBC is representing red blood cells and the main function of red blood cells is to transport oxygen. Red blood cell is the most common type of blood cell and it is very important in human life and good function of the human body.
That transportation is starting from the lungs and it goes to the tissues.
When it comes to tissues, there it is used as a source of electrons and also ATP synthesis that is found in mitochondria.