根据以下材料，回答 BaekelandandHartmannreportthatthe"shortsleepers"hadbeenmoreorlessaverageintheirsleepneedsuntilthemenwereintheirteens.Butataboutage15orso,themenvoluntarilybegancuttingdowntheirnightlysleeptimebecauseofpressuresfromschool,work,andotheractivities.Thesementendedtoviewtheirnightlyperiodsofunconsciousnessasbothersomeinterruptionsintheirdailyroutines. Ingeneral,these"shortsleepers"appearedambitious,active,energetic,cheerful,conformistintheiropinions,andverysureabouttheircareerchoices.Theyoftenheldseveraljobsatonce,orworkedfull-orpart-timewhilegoingtoschool.Andmanyofthemhadastrongurgetoappear"normal"or"acceptable"totheirfriendsandassociates. Whenaskedtorecalltheirdreams,the"shortsleepers"didpoorly.Morethanthis,theyseemedtoprefernotremembering.Insimilarfashion,theirusualwayofdealingwithpsychologicalproblemswastodenythattheproblemexisted,andthentokeepbusyinthehopethatthetroublewouldgoaway. Thesleeppatternsofthe"shortsleepers"weresimilarto,butlessextremethan,sleeppatternsshownbymanymentalpatientscategorizedasmanic. The"longsleepers"werequitedifferentindeed.BaekelandandHartmannreportthattheseyoungmenhadbeenlengthysleepssincechildhood.Theyseemedtoenjoytheirsleep,protectedit,andwerequiteconcernedwhentheywereoccasionallydeprivedoftheirdesired9hoursofnightlybedrest.Theytendedtorecalltheirdreamsmuchbetterthandidthe"shortsleepers." Manyofthe"longsleepers"wereshy,anxious,introverted,inhibited,passive,mildlydepressed,andunsureofthemselves(particularlyinsocialsituations).Severalopenlystatethatsleepwasanescapefromtheirdailyproblems. Accordingtothereport,___________.
A.many short sleepers need less sleep bynature B.many short sleepers are obliged toreduce their nightly sleep time because they are busy with their work C.long sleepers sleep a longer period oftime during the day D.many long sleepers preserve theirsleeping habit formed during their childhood正确答案D
