Newborn Babies Weighing Less Than 4 Pounds at Birth Are

Newborn babies weighing less than 4 pounds at birth are at considerable risk for eventual mental retardation and various behavior problems. Which of the following seems to be most responsible for this relationship?

A) These babies inherit a weak genetic structure from their father.
B) Hospitals give small babies less attention, on average, than larger babies.
C) Most small babies have Down syndrome or other identifiable medical disorders linked to brain malformation.
D) Mothers of low-weight babies tend to be young or poor and unlikely to get proper medical or nutritional care for themselves or the babies.