Which of the Following Represents the Selective Placement Confound Associated

Which of the following represents the selective placement confound associated with adoption studies?

A) Children who are adopted may have other psychological disturbances that influence IQ.
B) Adoptive children may have experienced lacking environments depending on time in foster care.
C) Adopted children may have more enriched environments than their biological counterparts.
D) Adoption agencies frequently place children in homes similar to those of the biological parents.