Which of the Following Studies Would NOT Be Used to Determine

Which of the following studies would NOT be used to determine the relative contribution of genetics to the expression of a trait or disorder?

A) Family studies,where researchers examine the extent to which a trait "runs" in an intact family
B) Twin studies,where researchers investigate whether identical twins are more alike on a psychological characteristic than are fraternal twins
C) Adoption studies,where adoption agencies frequently place children in homes similar to those of the biological parents
D) All of the above studies would be used.