Mark and Mathew Are Identical Twins Who Developed from Asingle

Multiple Choice

Mark and Mathew are identical twins who developed from asingle zygote and share identical DNA. Nevertheless, as they develop, differences in physical and psychological characteristics become evident. These differences are due to:

A) each twin's unique genetic blueprint.
B) pruning of unused neurons in each child's brain.
C) allele variation.
D) epigenetic change.