Several years into a campaign to get kids to eat better and exercise more, child obesity rates have appeared to stabilize, and might be poised for a reversal. But a study published Monday in the journal PNAS suggests that among adolescents, the【C1】______ signs are limited to those from better-educated, more【C2】______families. Among teens from poorer, less well-educated families, obesity has【C3】______to rise. That class-gap was not【C4】______in younger children. But as children neared【C5】______, the class differences became increasingly obvious. 【C6】______between rich and poor in obesity rates are not new, and they are only one of many health gaps that make poor patients sicker and more likely to die【C7】______than richer ones. But if the public health message on obesity "has not diffused【C8】______across the population," this gap could【C9】______efforts to stem a tidal wave of【C10】______obesity-related diseases in the years ahead. Researchers from Harvard University"s Kennedy School of Government found that【C11】______ activity may account largely for the【C12】______ trend in obesity between rich and poor. If public health experts are to prevent childhood obesity and【C13】______drive down future obesity among adults, they"ll have to figure out【C14】______less advantaged kids don"t get as much exercise, the authors of the latest study say. Yes, lack of【C15】______centers, playgrounds, and streets and sidewalks that【C16】______walking, biking and playing are important, they wrote. But, they added, "this is not the whole story." Among children with parents who【C17】______high on the socioeconomic scale, participation in high school sports and clubs has increased. But among their【C18】______from families of lower educational【C19】______and income, such participation has【C20】______. 【C5】

A. adulthood
B. childhood
C. fatherhood
D. neighborhood