How Can a Blastocyst,which Is Basically a Mass of Cells,develop

Multiple Choice

How can a blastocyst,which is basically a mass of cells,develop into different tissues,organs,systems,and ultimately a fetus?

A) Chemicals enter the cells,causing them to become different tissues.
B) Chemical signals cause the production of genes.
C) Chemical signals cause the regulation of genes and production of particular proteins.
D) Chemical signals cause the regulation of proteins that will produce the appropriate genes.
E) Chemical signals cause all cells to develop into one type of organ that splits off into all the organs of the body.