单选题：Questions are based on the following passage. Child psycholo

Questions are based on the following passage.
Child psychologists--and kindergarten teachers--have long known that when children first show up for school，some of them speak a lot more fluently than others．Psychologists also know that children’s socioeconomic status tends to be closely connected with their language facility．The better off and more educated a child’s parents are，the better vocabulary ability that child tends to have by school age—and vocabulary skill is a key predictor for success in school．Children from low-income families，who may often start school knowing significantly fewer words than their better-off peers，will struggle for years to make up that ground.
Previous studies have shown that wealthier，educated parents talk to their young children more，using more complex vocabulary and sentences，than parents of lesser means．And these differences may help explain why richer kids start school with richer vocabularies．But what goes on before children can talk．during that phase--familiar to any parent--when communication takes the form of pointing，waving，grabbing and other kinds of baby sign language? Do well--off parents also gesture more to their kids?
Indeed they do，say psychologists Susan Gold in-Meadow and Meredith Rowe of the University of Chicago．The researchers found that at 14 months of age, babies already showed a wide range of “speaking” ability through gestures, and that those differences were closely linked with their socioeconomic back ground and how frequently their parents used gestures to communicate．High-income，better-educated parents gestured more frequently to their children to convey meaning and new concepts, and in turn，their kids gestured more to them．When researchers tested the same children at 54 months of age, they found that those early gesturers turned out to have better vocabulary ability than other students.
At 14 months of age, researches say, pointing toward an object is the way most kids use gestures．If a parent responds to that gesture by identifying the object in words—by sayin9， “That’s a doll，”for example--children get a head start on growing their original vocabularies.“That’s a teachable moment．And mothers are teaching the kids the word for an object.” says Gold in-Meadow.
Psychologists have found that children’s language ability largely depends on——. A．their family’s socioeconomic background
B．their successful performance in school
C．their education background before school
D．their own personality