A group of researchers wanted to find out whether trait X was primarily determined by genetics or environment. They examined the similarity in trait X between pairs of 1) monozygotic twins raised in the same households; 2) monozygotic twins raised in different households; 3) dizygotic twins raised in the same households; and 4) dizygotic twins raised in different households.
a) If trait X was primarily determined by genetics, which group(s) of twins would show the highest similarity in trait X? Explain your answer.