Cells are the basic unit of life. Thus, cells are responsible for maintaining a stable internal environment within living organisms. How do humans continue to maintain a stable internal environment if billions of cells die within their bodies each day?
A.
New cells are eaten in the form of food.
B.
The cells must be able to reproduce.
C.
Exposure to the Sun stimulates cell growth.
D.
Humans need fewer cells as they get older.