Question

Growth factors that are transported through the blood play what role in the cell cycle?
an internal signal that tells the cell to stop dividing and repair its DNA
an internal signal that functions as an executioner
an internal signal to tell the cell which stage of the cell cycle to enter next
an external signal to tell the cell how long it should spend in each phase of the cell cycle
an external signal to tell the cell whether or not to divide

Answer 1

an eternal signal to tell the cell whether or not to divide

Answer 2

*external