Substantial Evidence Suggests That Differentiation Signals Influence the Developmental Pathway

Substantial evidence suggests that differentiation signals influence the developmental pathway taken by stem cell daughter cells. From what sources might these signals arise?

A) the presence of specific adhesion molecules on neighboring cells
B) the internal genetic program inherited from the dividing adult stem cell itself
C) variations in the concentration of signal molecules involved in a signal transduction pathway
D) All of the above are reasonable hypotheses.