Mark and Mathew Are Identical Twins Who Developed from a Single

Multiple Choice

Mark and Mathew are identical twins who developed from a single 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.