Mostforestfiresarecausedbyhumancarelessness,negligence,orignorance.Forestfireprevention,therefore,ismainlyaproblemofcreatingabetterunderstandingoftheimportanceofforests,anawarenessofthedangeroffireinthewoods,andasenseofpersonalresponsibilitytosafeguardtheforestsfromdanger.Thisisnotaneasyjob.Acitydweller,usedtopavedstreet,doesnoteasilychangehissmokinghabitswhenhegoesintothewoods.
Carelesssmokersareresponsibleforthousandsofforestfireseachyear.Manyofthesearestartedwhencigarettebuttsandmatchesaretossedfromautomobiles.Othersarecausedbyhunters,hikers,fishermen,orwoodsworkerswhoarecarelessindisposingoftheirsmokingmaterial.TheForestServicehaspostedrulesinmanyoftheNationalForeststhatprohibitsmokingexceptincertaindesignatedareas.Manyofthestateshavelawsagainstthrowinglightedmaterialsfromautomobiles.Thepreventionofsmoker-causedfires,however,dependsuponchangingtheattitudesandbehaviorofmillionsofpeoplewhosmokeinhazardousarea.
Themostimportantnaturalcauseoffireislightning.Thisaccountsfor11percentofforestfiresonprotectedlandfortheentirenation.Inthewesternstates,lightningcausesamuchhigherpercentageoffirethanitdoesintheeast.
Advancesinknowledgeoffireweatherarehelpingforestprotectionforcestoknowwhentobealertforlightning-causedfires.Adequateandwell-equippedforcescancontrolthemquicklyandholdthedamagetoaminimum.Experimentsin“seeding”thundercloudstopreventorcontrolthelightningitselfhavebeeninprocessformanyyears,butnewbreakthroughsareneededforanysignificantreductioninthelightningstarts.
1.Thepassageischieflyabout
A.smokinginforests
B.thechiefcauseofforestfireandtheirprevention
C.changingtheattitudesandbehaviorofmillionsofpeople
D.advancesinknowledgeoffireweather
2.Preventingsmoker-causedforestfiresismainlyaproblemof——.
A.buildingtheproperknowledgeandhabitsinhumanbeings
B.safeguardingtheforestfromfire
C.postingrulesinforests
D.holdingthedamagetominim
![定义：对于任意x∈[0，1]，函数f（x）≥0恒成立，且当x1≥0，x2≥0，x1+x2≤1时，总有f（x1+x2）≥f（x1）+f（x2）成立，则称f（x）为G函数．已知函数g（x）=x2与h（x）=a-2x-1是定义在[0，1]上的函](/UploadFile/wdimg/2071/3070918770/87/3398667814.jpg)
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