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高一英语阅读专项：限时阅读--科普说明Analtimeterisaninstrumentusedinanairplanetotellthepilothowhighheisflying.Thealtimeterusedinmostairplanesisakindofbarometerwhichmeasuresairpressure.Atsealevelthispressureismorethan14poundsoneverysquareinchofthesurface.Thehigheryougointotheair,thelowertheairpressureis.Analtimetermeasuresthisairpressuretoshowhowhightheairplaneisabovethesealevel.Butthealtimeterdoesnotshowhowhightheplaneisabovetheground.Aplanemightbeflyingataheightof15,000feet,butitwouldbeonlyathousandfeetorsoabovethegroundifthelandinthatareahappenedtobe14.000feetabovethesealevel.Thepilotadjusts(调整)hisaltimetertotheactualsea-levelpressurebeforeleavingtheairportandhecorrectsitinflightbynewinformationgiventohimbyradio.Heflieshighenoughtoaboveanymountainhemaypassonhiscourse.Thebarometeraltimeteriscorrectwithinabove300feet.Anotherkindofaltimeter,theradioaltimeter,makesuseofradioreflection.Itcalculatestheheightoftheflyingplanebysendingoutelectricalsignalstothesurfacebelowandmeasuringthetimerequiredforthemtobounce(弹)back.Itiscorrectwithin1-5feetoverwater,butitisnotreliableoveruneven(不平的)land.Bigplanesusuallyhavebothkindsofaltimeters.1.Thefollowingdrawingshowsaplaneflyingoveramountain,whichoftheheightsisgivenbythebarometeraltimeterintheplaneatthesamemoment?2.Thebarometeraltimeterwon'tworkiftheplaneflies______.A.beyondtheatmosphereB.aboveveryhighlandC.oververyunevengroundD.with1,000feetoftheground3.Supposeaplaneusingaradioaltimeterisflying10,000metersaboveahighlandwhichis4,000metersabovethesealevel.Whatreadingwillbegivenbythealtimeter?A.10,000meters.B.4,000meters.C.14,000meters.D.6,000meters.4.Supposeaplaneusingbothkindsofaltimetersisflyingoveramountainousareawherethelandrisesandfallsveryabruptly(陡峭的).Thepilotkeepshisplanesteadyatthesameheight.Whichkindofreadingwillyougetoneachofthealtimeters?A.Thereadingsonbothaltimeterswillremainsteady.B.Thereadingsonbothaltimeterswillriseandfallabruptly.C.Thereadingonthebarometeraltimeterwillriseandfallabruptly,whilethatontheradioaltimeterwillremainsteady.D.Thereadingontheradioaltimeterwillriseandfallabruptly,whilethatonthebarometeraltimeterwillremainsteady.参考答案：CAAD