The Following Studies Determine How Much Genetics Contributes to the Expression

The following studies determine how much genetics contributes to the expression of that trait or disorder except

A) twin studies where researchers investigate whether identical twins are more alike on a psychological characteristic,like intelligence or extraversion,than are fraternal twins,and thus can infer that this characteristic is genetically influenced.
B) family studies where researchers examine the extent to which a trait "runs" or goes together in intact families,those in which all family members are raised in the same home.
C) adoption studies where adoption agencies frequently place children in homes similar to those of the biological parents.
D) studies of fraternal twins compared across pairs raised in the same versus different environments.