The Most Significant Threat to the Usefulness of Twin Studies

Multiple Choice

The most significant threat to the usefulness of twin studies is the fact that the majority of monozygotic twins

A) do not share the same amniotic sac during prenatal development.
B) do not develop from the same zygote.
C) develop from two separate eggs that are fertilized by two separate sperms.
D) always share 100 percent of the same DNA.