Which Six-Year-Old Child Would Be Most Likely to Experience an Increase

Which six-year-old child would be most likely to experience an increase in IQ over the next few years

A)  Darius, who continues living with his loving middle-class biological parents 
B)  Aron, who continues living in an understaffed orphanage 
C)  Ceili, who was recently adopted from an understaffed orphanage by loving middle-class parents 
D)  Bettina, who recently started living in an understaffed orphanage following the death of her parents