题目内容：
Questionsarebasedonthefollowingpassage.
ThehumanimpactontheAmazonrainforesthasbeengrosslyunderestimatedaccordingtoresearchersfromBrazilandtheUK.
Theyfoundthatselectivelogging(砍伐树木)andsurfacewildfirescanresultinanannuallossof54billiontonnesofcarbonfromtheBrazilianAmazon,increasinggreenhousegasemissions.Thisisequivalentto40%oftheyearlycarbonlossfromdeforestation(砍伐森林)--whenentireforestsarechoppeddown.
Thisisthelargesteverstudyestimatingtheaboveandbelow-groundcarbonlossfromselectiveloggingandgroundlevelforestfiresinthetropics,basedondatafrom70,000sampledtreesandthousandsofsoil,rubbishanddeadwoodsamplesfrom225sitesintheeasternBrazilianAmazon.
Theforestdegradation(退化)oftenstartswithloggingofprizedtrees.
Oncetheforesthasbeenlogged,themanygapsinthecanopy(林冠)meansitbecomesmuchdrierduetoexposuretothewindandsun,increasingtheriskofwildfiresspreadinginsidetheforest.
Thecombinationofselectiveloggingandwildfiresdamagesturnsprimaryforestsintoathickscrub(发育不良的矮树丛)fullofsmallertreesandplants,whichstores40%lesscarbonthanundisturbedforests.
Sofar,climatechangepoliciesonthetropicshaveeffectivelybeenfocusingonreducingcarbonemissionsfromdeforestationonly,notaccountingforemissionscomingfromforestdegradation.
LeadresearcherDr.ErikaBerenguerfromLancasterUniversitysaid,"Theimpactsoffireandloggingintropicalforestshavealwaysbeenlargelyoverlookedbyboththescientificcommunityandpolicymakerswhoareprimarilyconcernedwithdeforestation.Yetourresultsshowhowthesedisturbancescanseverelydegradetheforest,withhugeamountsofcarbonbeingtransferredfromplantmatterstraightintotheatmosphere."
Thesecondauthor,Dr.JoiceFerreirafromEmbrapainBrazil,said,"OurfindingsalsodrawattentiontothenecessityforBraziltoimplementmoreeffectivepoliciesforreducingtheuseoffireinagriculture,asfirescanbothcompletelydestroyprivateproperty,andescapeintosurroundingforestscausingwidespreaddegradation.Bringingfireandillegalloggingundercontroliskeytoreachingournationalcommitmenttoreducingcarbonemissions."
WhatisthepossibleresultofselectiveloggingandsurfacewildfiresintheAmazonrainforest? A．Morecarbonisreleased.
B．Moregreenhousegasisreleased.
C．Thewholeforestgetscutdown.
D．45billiontonnesofcarbonislost.
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