Twelve-Year-Old Heather Has a Smaller Head Circumference and Less Gray

Multiple Choice

 Twelve-year-old Heather has a smaller head circumference and less gray matter thickness than typical children of her same age, sex, and size. It is most likely that

A) Heather's mother used alcohol or other drugs during her pregnancy.
B) Heather's mother has PKU.
C) Heather has PKU.
D) Heather has fragile-X syndrome.