Do you wake _21__very day feeling too tired,or even upset?If so,then a new alarm clock could be just

题目

Do you wake _21__very day feeling too tired,or even upset?If so,then a new alarm clock could be just for you.
The clock,called Sleep smart,measures your sleep cycle,and waits__22_you to be in your lightest phase of sleep__23_rousing you.Its makers say that should_24__you wake up feeling refreshed every morning.
As you sleep you pass__25_a sequence of sleep states—light sleep,deep sleep and REM(rapid eye movement) sleep---that__26_approximately every 90 minutes.The point in that cycle at which you wake can_27__how you feel later,and may_28__have a greater impact than how much or little you have slept.Being roused during a light phase__29_you are more likely to wake up energetic.
SliipSmart_30__the distinct pattern of brain waves _31__during each phase of sleep,via a headband equipped_32__electrodes and a microprocessor.This measures the electrical activity of the wearer’s brain,in much the_33__way as some machines used for medical and research_34__and communicates wirelessly

答案

a
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a
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c
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d
c
a
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a
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a