Q. a) A group of researchers wanted to find out whether trait X was primarily determined by genetics or environment. They examined similarity in trait X between pairs of 1) monozygotic twins raised in same households; 2) monozygotic twins raised in different households; 3) dizygotic twins raised in same households; also 4) dizygotic twins raised in different households.

b) If trait X was primarily determined by environment, which group(s) of twins would show highest similarity in trait X? Explain your answer.