Kayla and Layla are twins who were separated at birth

A researcher interested in studying heredity tracks them down and speaks to their different families about the benefits that can be achieved by studying the two young girls. The girls and their different sets of parents agree to participate, and studies begin assessing various areas of the girls' lives. In order for this type of twin study to be most effective, what kind of twins should Kayla and Layla be?
A) conjoined
B) monozygotic
C) amorphous
D) dizygotic

Answer: B