The period of prenatal development that begins about three weeks after fertilization is known as:
a. the embryonic stage.
b. the fetal stage.
c. the implantation stage.
d. the zygotic stage.
Question 2
The process by which genes and the environment interact, turning on certain genes, is known as:
a. embryonic development.
b. epigenetics.
c. fertilization.
d. teratogenic interaction.