True because you would need to put up an ad saying "kidney donor needed" or "blood donor needed" if you didn't do that you would most likely be stuck with no donor unless a friend or family member donates
A.
The endurance of an athlete is dependent on his or her body's ability to uptake oxygen efficiently, a task carried out by the red blood cells.
Its called a chain reaction because its just like two or three elements that help to make something