How do cells in organisms vary?

All cells has the same DNA but sum are different The differences depend on what parts of the DNA the cell uses in a process called gene expression. Gene expression can be influenced by environmental factors, and influences from the environment can further affect the phenotype in other ways.

Explanation:

Gene expression depends on a constant dialogue between the nucleus and the cytoplasm by University of Geneva Gene expression is the process by which genetic information is used to produce proteins, which are essential for cells to function properly and fulfil their many purposes.

51% were unhappy, i think .   ; )

answer; i do believe its (b) 12.5 years of age;