The more parents talk to their children, the faster those children"s vocabularies grow and the better their intelligence develops. In 1995, Betty Hart and Todd Risley of the University of Kansas found a close【C1】______between the number of words a child"s parents had spoken to him【C2】______the time he was three and his【C3】______success at the age of nine. At three, children born into professional families had【C4】______30m more words than those from a poorer background. This observation has profound【C5】______for policies about babies and their parents. It suggests that sending children to "preschool" (【C6】______or kindergartens) at the age of four—a favored【C7】______among policymakers—comes too late to【C8】______for educational shortcomings at home.【C9】______, understanding of how children"s vocabularies develop is growing. One of the most striking【C10】______came from Anne Fernald, who has found that the difference【C11】______well before a child is three. Even at the【C12】______age of 18 months, when most toddlers speak only a dozen words, those from【C13】______families are several months behind other more favored children. 【C14】______, Dr Fernald thinks the differentiation starts at birth. She 【C15】______ how quickly toddlers process language by sitting them on their mothers" laps and showing them two images; a dog and a ball. A recorded voice tells the toddler to look at the ball while a camera records his【C16】______. This lets Dr Fernald【C17】______the moment the child"s gaze begins【C18】______towards the correct image. At 18 months, toddlers from【C19】______backgrounds can identify the correct object in 750 milliseconds—200 milliseconds faster than those from poorer families. This, says Dr Fernald, is a【C20】______difference. 【C5】

A. implications
B. manipulations
C. supervisions
D. requirements