If all cells in a developing organism have identical DNA, how can a stem cell give rise to many types of differentiated cells?

A. The single strand of DNA causes all cells to grow together, but mutations in the DNA cause cells to form new types at random.

B. During the process of differentiation, whichever portions of the single DNA strand are activated the fastest, will dictate the type of cell it becomes.

C. The single strand of DNA causes all cells to grow at the same rate, but the function of the cell will change depending on the number of copies of DNA contained in the nucleus of each cell.

D. During the process of differentiation, only specific portions of the single DNA strand are activated to create a new cell, and the new type of cell it becomes depends on the portion of the DNA that is activated.