How do cigarettes and radiation cause cancer?

Cancer is caused by the loss of cell cycle control. Basically excess cell division or deficient apoptosis (killing off of a cell).
Cigarettes and radiation mess with the normal receptors for growth factors. When they become mutated, there is a loss of control and cause cancer when they are introduced into a cell. They permanently turn on the receptors for growth factors.
So, cancer could be the over-expression of the genes that stimulate cell division… Or, cancer could be the inactivation of tumor suppressor genes that prevent the cell from dividing or promote apoptosis.
In short, Cigarettes and radiation cause mutations.
Yet,
None of the answers really look appealing. But, I’d answer E since its the only choice that mentions the cell cycle which is all important when looking at cancer.