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.IthasdriftedacrosstheCanadianArcticand

　　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”.

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　　74.Whatcouldhappentothenorthmagneticpolebythemiddleofthe21stcentury?(回答词数不超过8个)

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　　75.Whatisthemainideaofthepassage?(回答词数不超过8个)

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