How many divisions of mitosis are required for a somatic cell to form 256 cells?

The correct option is D 8
Each mitotic cell division gives rise to two daughter cells. Cell division is exponential i.e., 1 parent cell gives rise to 2 daughter cells. Then, each of the 2 cells produced, divide to produce 2 cells each, making a total of 4 cells. Again, 4 cells divide to produce 2 cells each, giving 8 cells in total. So, only 8 mitotic divisions are required for a somatic cell to form $256\left(2^8\right)$ cells.