北京市海淀区2016届高考英语完形填空和阅理暑假自练（6）阅读下列四篇短文，从每小题后所给的A,B,C或D四个选项中，选出最佳选项。Belowisaselectionfromapopularsciencebook.Ifbloodisred，whyareveins(静脉)blue?Actually，veinsarenotblueatall.Theyaremoreofaclear，yellowishcolour.Althoughbloodlooksredwhenit'soutsidethebody，whenit'ssittinginaveinnearthesurfaceoftheskin，it'smoreofadarkreddishpurplecolour.Attherightdepth，thesebloodfilledveinsreflectlessredlightthanthesurroundingskin，makingthemlookbluebycomparison.Whichworksharder，yourheartoryourbrain?Thatkindofdependsonwhetheryou'rebusythinkingorbusyexercising.Yourheartworksuptothreetimesharderduringexercise，andshiftsenoughbloodoveralifetimetofillasupertanker.But，inthelongrun，yourbrainprobablytipsit，becauseevenwhenyou'resittingstillyourbrainisusingtwiceasmuchenergyasyourheart，andittakesfourtofivetimesasmuchbloodtofeedit.Whydoteethfallout，andwhydon'ttheygrowbackingrownups?Baby(or“milk”)teethdonotlastlong；theyfallouttomakeroomforbigger，strongeradultteethlateron.Adultteethfalloutwhentheybecomedamaged，decayedandinfectedbybacteria.Oncethissecondsetofteethhasgrownin，you'redone.Whenthey'regone，they'regone.Thisisbecausenaturefiguresyou'resetforlife，andwhatcontrolsregrowthofyourteethswitchesoff.Dooldpeopleshrinkastheyage?Yesandno.Manypeopledogetshorterastheyage.But，whentheydo，itisn'tbecausethey'reshrinkingallover.Theysimplyloseheightastheirspine(脊柱)becomesshorterandmorecurvedduetodisuseandtheeffectsofgravity(重力)．Many(butnotall)menandwomendoloseheightastheygetolder.Menloseanaverageof34cminheightastheyage，whilewomenmaylose5cmormore.Ifyoulivetobe200yearsold，wouldyoukeepshrinkingtillyouwere，like60cmtall，likealittleboyagain？No，becauseoldpeopledon'treallyshrink！Itisnotthattheyaregrowingbackwards—theirlegs，armsandbackbonesgettingshorter.Whentheydogetshorter，it'sbecausethespinehasshortenedalittle.Or，moreoften，becomemorebentandcurved.Whydoesspinningmakeyoudizzy(眩晕的)?Becauseyourbraingetsconfusedbetweenwhatyou'reseeingandwhatyou'refeeling.Thebrainsensesthatyou'respinningusingspecialgravityandmotion-sensingorgansinyourinnerear，whichworktogetherwithyoureyestokeepyourvisionandbalancestable.But，whenyousuddenlystopspinningthesystemgoesoutofcontrol，andyourbrainthinksyou'removingwhileyou'renot!Wheredofeelingsandemotionscomefrom?Mostlyfromanancientpartofthebraincalledthelimbicsystem.Allmammalshavethisbrainarea—frommicetodogs，cats，andhumans.Soallmammalsfeelbasicemotionslikefear，painandpleasure.Butsincehumanfeelingsalsoinvolveother，newerbitsofthebrain，wefeelmorecomplexemotionsthananyotheranimalontheplanet.Ifexercisewearsyouout，howcanitbegoodforyou?Becauseourbodiesadapttoeverythingwedotothem.Andasfarasyourbodyisconcerned，it's“useit，orloseit”！It'snotthatexercisemakesyouhealthy；it'smorethatalackofexerciseleavesyourbodyweakandeasilyaffectedbydisease.1．Whatisthecolourofbloodinaveinnearthesurfaceoftheskin?A．Blue.B．Lightyellow.C．Red.D．Darkreddishpurple.解析细节理解题。根据第一个标题下的“...it'smoreofadarkreddishpurplecolour.”可知答案。答案D。2．Whydosomeoldpeoplelookalittleshrunkenastheyage?A．Becausetheirspineisinactiveuse.B．Becausetheyaremoreeasilyaffectedbygravity.C．Becausetheykeepgrowingbackwards.D．Becausetheirspinebecomesmorebent.解析细节理解题。根据第四个标题下的“Theysimplyloseheightastheirspine(脊柱)...
