Which of the Following Reduces the Value of Twin Studies

Multiple Choice

Which of the following reduces the value of twin studies as evidence for the role of heredity in determining IQ?

A) Children tend to be adopted by people who are fairly similar to their natural parents.
B) There have been so many studies of pairs of identical twins who were separated at birth that the results are unclear.
C) Identical twins do not share the same prenatal environment.
D) Identical twins who were not reared together usually have very different IQ scores.