The NICHD Study of Early Child Care and Youth Development has found all of the following except

a. childcare jeopardizes the infant-parent attachment relationship only when the care is not optimal and the mother is not sensitive in her interactions with her infant
b. infants in high-quality childcare tend to have fewer behavior problems at two and three years of age than infants in poor quality childcare
c. infants and toddlers in high-quality childcare tend to have more advanced language development than infants and toddlers in poor quality childcare
d. even when childcare is high quality, it has few positive effects on the cognitive development of low-income infants and toddlers

D