As it is, sleep is so undervalued that getting by on fewer hours has become a badge of honor.Plus, we live in a culture that（36）to the late-nighter, from 24-hour grocery stores to onlineshopping sites that never close.It's no surprise, then, that more than half of American adults don't getthe 7 to 9 hours of shut-eye every night as（37）by sleep experts.
　　Whether or not we can catch up on sleep--on the weekend, say--is a hotly（38）topic amongsleep researchers.The latest evidence suggests that while it isn't（39） , it might help.When Liu, theUCLA sleep researcher and professor of medicine, brought  40   sleep-restricted people into the labfor a weekend of sleep during which they logged about 10 hours per night, they showed（41)in theability of insulin (胰岛素) to process blood sugar.That suggests that catch-up sleep may undo some but not all of the damage that sleep（42）causes, which is encouraging, given how many adults don'tget the hours they need each night.Still, Liu isn't（43）to endorse the habit of sleeping less andmaking up for it later.
　　Sleeping pills, while helpful for some, are not（44） an effective remedy either."A sleeping pillwill（45）one area of the brain, but there's never going to be a perfect sleeping pill, because youcouldn't really replicate (复制 ) the different chemicals moving in and out of different parts of the brainto go through the different stages of sleep," says Dr.Nancy Collop, director of the Emory UniversitySleep Center.

A.alternatively
B.caters
C.chronically
D.debated
E.deprivation
F.ideal
G.improvements
H.necessarily
I.negotiated
J.pierce
K.presumption
L.ready
M.recommended
N.surpasses
O.target
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