简答题(共3小题；每小题2分，满分6分)阅读下面短文，根据第73至第75小题的具体要求，简要回答问题。Thenorthmagneticpole(磁极)isnolongeraresidentofCanada.IthasdriftedacrosstheCanadianArcticandisnowanglingtowardSiberia.NottobeconfusedwiththegeographicNorthPole—thenorthernextremityoftheEarth’saxis(地轴),thenorthmagneticpole(wheretheEarth’smagneticfieldisdirecteddownward)ismovingduetonaturalchangesintheEarth’smagneticfield,aprocessthatoriginatesabout3000kilometersbelowourfeet,intheoutercore(核心)oftheplanet.Butscientistsarenownoticingthatthemagneticpolehaspickedupitspace.Overthepastcentury,thepolehasbeenmigratingatanaveragespeedofabout10kilometersperyear,saysLarryNewitt,headofGeomagneticLaboratoryatNaturalResourcesCanadainOttawa.Sincethe1970s,thisspeedhasincreasedtoabout50kilometersperyear.Scientistsarewonderingwhythespeedisincreasing,saysNewitt.Onehypothesis(假说)relatesitto“magneticjerks”,suddenshifts(变化)intherateofchangeofthemagneticfield.Therehavebeenthreejerksinthepastfourdecades,eachonecorrelatingtoanincreasesinspeed.Ifthenorthmagneticpolecontinuesatitscurrentrate,itcouldreachSiberiaby2056.“Formostofrecordedhistory,thepolehasbeenapartofCanada,andnowit’snot,”saysNewitt.“Itmaybeablowtoourcollectivepsyche,butotherthanthat,itdoesn’thaveamajoreffectonmostpeople’sexistence.”73.Findinthepassageawordclosestinmeaningtotheunderlinedword“angling”.____________________________________________________________74.Whatcouldhappentothenorthmagneticpolebythemiddleofthe21stcentury?(回答词数不超过8个)____________________________________________________________75.Whatisthemainideaofthepassage?(回答词数不超过8个)____________________________________________________________
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