（2010·广东华南师大附中高三综合测试一）

Judgingfromrecentsurveysmostexpertsinsleepbehaviouragreethatthereisvirtuallyanepidemic（流行病）ofsleepinessinthenation.“Ican’tthinkofasinglestudythathasn’tfoundAmericansgettinglesssleepthantheyoughtto”saysDr.David.Evenpeoplewhothinktheyaresleepingenoughwouldprobablybebetteroffwithmorerest.

Thebeginningofoursleep-deficit（lack）crisescanbetracedbacktotheinventionofthelightbulbacenturyago.Fromdiaryentriesandourpersonalaccountsfromthe18thand19thcenturiessleepscientistshavereachedtheconclusionthattheaveragepersonusedtosleepabout9.5hoursanight.“Thebestsleephabitsoncewereforcedonuswhenwehadnothingtodointheeveningdownonthefarmanditwasdark.”Bythe1950sand1960sthesleepschedulehadbeenreduceddramaticallytobetween7.5and8hoursandmostpeoplehadtowaketoanalarmclock.“Peoplecheatintheirsleepandtheydon’tevenrealizethey’redoingit”saysDr.David.“Theythinkthey’reokeybecausetheycangetbyon6.5hourswhentheyreallyneed7.58orevenmoretofeelideallyenergetic.”

Perhapsthemostmercilessrobberofsleepresearchessayisthecomplexityoftheday.Wheneverpressuresfromworkfamilyfriendsandcommunityincreasemanypeopleconsidersleeptheleastexpensiveitemontheirprogramme.“Inoursocietyyou’reconsidereddynamicifyousayyouneedonly5.5hours’sleep.Ifyou’vegottoget8.5hourspeoplethinkyoulackdriveandambition.”

Todeterminetheconsequencesofsleep-deficitresearchershaveputsubjectsthroughasetofpsychologicalandperformancetestsrequiringthemforinstancetoaddcolumnsofnumbersorrecallapassagereadtothemonlyminutesearlier.“We’vefoundthatifyou’reinsleepdeficitperformancesuffers”saysDr.David.“Short-termmemoryisweakenedasareabilitiestomakedecisionsandtoconcentrate.”

41.Whatisthemaintopicofthepassage?

A.Researchonthecausesandconsequencesofsleep-deficit.

B.Theepidemicofsleepinessinthemoderntimes.

C.Thehistoryofpeople’ssleepingpatterns.

D.Theminimumofoursleepinghours.

42.WhichofthefollowingisDr.David’sopinion?

A.Peoplewhothinktheyare