Answer: C) As cells become more numerous, the amount of required growth factors and nutrients per cell becomes insufficient to allow for cell growth.
Explanation:
Growth factors are proteins that stimulate cell division.Two of the most important internal factors are kinases and cyclins. In most mammal cells stop dividing once they touch other cells this means that when a cell population reaches a certain density, the amount of required growth factors and nutrients available to each cell becomes insufficient to allow continued cell growth.