题目内容：
根据以下材料，回答题 LungCancer
Thedeathrateduetocancerofthelungshasincreasedmorethan800percentinmalesandhasmorethandoubledinfemalesduringthelast25years.Itisconsiderablyhigherinurbanandindustrialareasthaninruraldistricts.（46）Thosefactorswhichhavebeenmentionedmostfrequentlyarethepresenceofforeignparticlesandotherirritantsintheair(smokeparticles,smog,exhaustfumes),andthesmokingofcigarettesandcigars.
（47）Amongheavysmokers--21to30cigarettesperday--themortalityratefromlungcancerisnearly17timestheratefromnonsmokers.Itisexpectedthedeathrateamongwomenwillincreaseasthepresenthighrateofsmokingamongwomenhasitseffect.
SometimescasesoflungcancerarediscoveredatthetimeanX-rayistakenforthepurposeofdetectingtuberculosis.（48）Earlydetectionisabsolutelyessentialifanypossibilityofcureistobemaintained.ModemX-raymachinesincompetenthandsposesuchslightdanger,atleasttothoseover40yearsofagethatthiswouldbemuchmorethanoffsetbytheadvantagesofdiscoveringatumorwhileitissmallenoughtobecompletelyremoved.
（49）Thetumormaygrowuntilthebronchusisblocked,cuttingoffthesupplyofairtothatlung.Thelungthencollapses,andthesecretionstrappedinthelungspacesbecomeinfected,witharesultingpneumoniaortheformationofalungabscess.（50）Theonlytreatmentthatoffersapossibilityofcure,beforesecondarygrowthshavehadtimetoform,istoremovethelungcompletely.Thisoperationiscalledpneumonectomy.
Malignanttumorsofthestomach,thebreast,theprostateglandandotherorgansmayspreadtothelungs,causingsecondarygrowths.
回答(46)题 A．Acommonformoflungcancerisbronchogeniccarcinoma,so-calledbecausethe
malignancyoriginatesinabronchus.
B．Lungcancer,alsoknownascarcinomaofthelungorpulmonarycarcinoma,isamalignantlungtumorcharacterizedbyuncontrolledcellgrowthintissuesofthelung.
C．Toooften,however,acurrentemphasisuponthedangerofexposuretoradiationfromX-raymachinescanfrightenpeopleawayfromroutinechestX-raysandthuspreventanearlydiagnosisoflungcancer.
D．Numerousstudieshavedemonstratedastrikingcorrelationbetweenthedeathratefromlungcancerandsmokinghabits.
E．Suchalungcancercanalsospreadtocausesecondarygrowthsinthelymphnodesofthechestandneckaswellasinthebrainandotherpartsofthebody.
F．Therearemanypossiblecauses,butitisstillcontroversialwhicharemostblameworthy.
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