What Role Do Epigenetic Tags Play in Differences Seen in Identical

What role do epigenetic tags play in differences seen in identical twins?

A) they alter the DNA of each identitical twin.
B) they influence the genes that determine gender role identification.
C) they combine to create a greater influence of the shared family environment as a determinant of personality.
D) they are chemical mechanisms that may activate or suppress certain genes to different degrees.
E) they determine how siblings will interact with each other.