阅读理解。
SupposewebuiltarobottoexploretheplanetMars.Weprovidetherobotwithseeingdetector(探
测器)tokeepitawayfromdanger.Itispoweredentirelybythesun.Shouldweprogramtherobotto
beequallyactiveatalltime?No.Therobotwouldbeusingupenergyatatimewhenitwasnotreceiving
any.Sowewouldprobablyprogramittostopitsactivityatnightandtowakeupatdawnthenext
morning.
Accordingtotheevolutionary(进化的)theoryofsleepevolutionequippeduswitharegularpattern
ofsleepingandwakingforthesamereason.Thetheorydoesn'tdenythat
sleepprovidessomeimportantrestorativefunctions.Itmerelysaysthatevolutionhasprogrammedusto
performthosefunctionsatatimewhenactivitywouldbeinefficientandpossiblydangerous.However
sleepprotectsusonlyfromthesortoftroublewemightwalkinto;itdoesn'tprotectusfromtroublethat
comeslookingforus.Sowesleepwellwhenweareinafamiliarandsafeplacebutwesleeplightlyifat
allwhenwefearthatbearswillnoseintothetent.
Theevolutionarytheoryexplainsthedifferencesinsleepamongcreatures.Whydocatsforinstance
sleepsomuchwhilehorsessleepsolittle?Surelycatsdonotneedfivetimesasmuchrepairand
restorationashorsesdo.Butcatscanaffordtohavelongperiodsofinactivitybecausetheyspendlittle
timeeatingandunlikelytobeattackedwhiletheysleep.Horsesmustspendalmostalltheirwakinghours
eatingbecausewhattheyeatisverylowinenergyvalue.Moreovertheycannotaffordtosleeptoolong
ortoodeeplybecausetheirsurvivaldependsontheirabilitytorunawayfromattackers.
1.Theauthorusedtheexampleoftherobotinspaceexplorationtotellus_____.
A.thedifferencesbetweenrobotsandmen
B.thereasonwhymenneedtosleep
C.abouttheneedforrobotstosaveenergy
D.aboutthedangerofmenworkingatnight
2.Evolutionhasprogrammedmantosleepatnightmainlytohelphim_____.
A.avoiddangerandineffectivelabor
B.restorehisbodilyfunctions
C.preventtroublethatcomeslookingforhim
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