单项选择题

As summer winds down, another new school year brings fresh notebooks, sharp pencils and-for many kids-a new cycle of sleep deprivation.
With classes that start as (62) as 7 a.m. and buses that pull (63) long before sunrise, some 80% of American kids in grades 6 through 12 are (64) short of sleep recommendations during the school year, according to research by the National Sleep Foundation, a sleep advocacy group.
(65) kids, studies suggest, struggle with depression.They gain (66) and get in more car accidents. Their grades suffer. (67) many turn to caffeine, with (68) results for productivity and unknown effects on the development of young brains.
Now, fueled by (69) research showing that adolescent bodies are designed to sleep late and that (70) school start times -even by just 30 minutes--makes a huge difference in how well teens feel and (71) , an increasing number of schools around the country are ringing morning (72) later than they used to. Many more are thinking about it.
At the same time, (73) , there are strong pockets of (74) to change from administrators and parents who think that bus schedules will get too complicated, that starting later will (75) with after-school programs or that kids simply will (76) later if they know they can sleep in a little more.
Despite the (77) involved in district- wide changes, sleep researchers emphasize the need to view sleep, like food and exercise, (78) a pillar of health.
"There are all these other things we do to (79) success for our kids, and getting them to have (80) sleep is probably one of the most important things you can do," says Judith Owens, a sleep researcher at Brown Medical School in Providence, R. I. "Parents need to take this as (81) as eating right, using seat belts and putting on sunscreen.\

81（）

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