2013年GMAT考试阅读模拟试题及答案3
<p> <span word="No">No</span> <span word="very">very</span> <span word="satisfactory">satisfactory</span> <span word="account">account</span> <span word="of">of</span> <span word="the">the</span> <span word="mechanism">mechanism</span> <span word="that">that</span> <span word="caused">caused</span> <span word="the">the</span> <span word="formation">formation</span> <span word="of">of</span> <span word="the">the</span> <span word="ocean">ocean</span> <span word="basins">basins</span> <span word="has">has</span> <span word="yet">yet</span> <span word="been">been</span> <span word="given">given</span>. <span word="The">The</span> <span word="traditional">traditional</span> <span word="view">view</span> <span word="supposes">supposes</span> <span word="that">that</span> <span word="the">the</span> <span word="upper">upper</span> <span word="mantle">mantle</span> <span word="of">of</span> <span word="the">the</span> <span word="earth">earth</span> <span word="behaves">behaves</span> <span word="as">as</span> <span word="a">a</span> <span word="liquid">liquid</span> <span word="when">when</span> <span word="it">it</span> <span word="is">is</span> <span word="subjected">subjected</span> <span word="to">to</span> <span word="small">small</span> <span word="forces">forces</span> <span word="for">for</span> <span word="long">long</span> <span word="periods">periods</span> <span word="and">and</span> <span word="that">that</span> <span word="differences">differences</span> <span word="in">in</span> <span word="temperature">temperature</span> <span word="under">under</span> <span word="oceans">oceans</span> <span word="and">and</span> <span word="continents">continents</span> <span word="are">are</span> <span word="sufficient">sufficient</span> <span word="to">to</span> <span word="produce">produce</span> <span word="convection">convection</span> <span word="in">in</span> <span word="the">the</span> <span word="mantle">mantle</span> <span word="of">of</span> <span word="the">the</span> <span word="earth">earth</span> <span word="with">with</span> <span word="rising">rising</span> <span word="convection">convection</span> <span word="currents">currents</span> <span word="under">under</span> <span word="the">the</span> <span word="mid">mid</span>-<span word="ocean">ocean</span> <span word="ridges">ridges</span> <span word="and">and</span> <span word="sinking">sinking</span> <span word="currents">currents</span> <span word="under">under</span> <span word="the">the</span> <span word="continents">continents</span>. <span word="Theoretically">Theoretically</span>, <span word="this">this</span> <span word="convection">convection</span> <span word="would">would</span> <span word="carry">carry</span> <span word="the">the</span> <span word="continental">continental</span> <span word="plates">plates</span> <span word="along">along</span> <span word="as">as</span> <span word="though">though</span> <span word="they">they</span> <span word="were">were</span> <span word="on">on</span> <span word="a">a</span> <span word="conveyor">conveyor</span> <span word="belt">belt</span> (<span word="conveyor">conveyor</span> <span word="belt">belt</span>: <span word="n">n</span>. 传送带) <span word="and">and</span> <span word="would">would</span> <span word="provide">provide</span> <span word="the">the</span> <span word="forces">forces</span> <span word="needed">needed</span> <span word="to">to</span> <span word="produce">produce</span> <span word="the">the</span> <span word="split">split</span> <span word="that">that</span> <span word="occurs">occurs</span> <span word="along">along</span> <span word="the">the</span> <span word="ridge">ridge</span>. <span word="This">This</span> <span word="view">view</span> <span word="may">may</span> <span word="be">be</span> <span word="correct">correct</span>: <span word="it">it</span> <span word="has">has</span> <span word="the">the</span> <span word="advantage">advantage</span> <span word="that">that</span> <span word="the">the</span> <span word="currents">currents</span> <span word="are">are</span> <span word="driven">driven</span> <span word="by">by</span> <span word="temperature">temperature</span> <span word="differences">differences</span> <span word="that">that</span> <span word="themselves">themselves</span> <span word="depend">depend</span> <span word="on">on</span> <span word="the">the</span> <span word="position">position</span> <span word="of">of</span> <span word="the">the</span> <span word="continents">continents</span>. <span word="Such">Such</span> <span word="a">a</span> <span word="back">back</span>-<span word="coupling">coupling</span>, <span word="in">in</span> <span word="which">which</span> <span word="the">the</span> <span word="position">position</span> <span word="of">of</span> <span word="the">the</span> <span word="moving">moving</span> <span word="plate">plate</span> <span word="has">has</span> <span word="an">an</span> <span word="impact">impact</span> <span word="on">on</span> <span word="the">the</span> <span word="forces">forces</span> <span word="that">that</span> <span word="move">move</span> <span word="it">it</span>, <span word="could">could</span> <span word="produce">produce</span> <span word="complicated">complicated</span> <span word="and">and</span> <span word="varying">varying</span> <span word="motions">motions</span>.</p><p> <span word="On">On</span> <span word="the">the</span> <span word="other">other</span> <span word="hand">hand</span>, <span word="the">the</span> <span word="theory">theory</span> <span word="is">is</span> <span word="implausible">implausible</span> <span word="because">because</span> <span word="convection">convection</span> <span word="does">does</span> <span word="not">not</span> <span word="normally">normally</span> <span word="occur">occur</span> <span word="along">along</span> <span word="lines">lines</span>, <span word="and">and</span> <span word="it">it</span> <span word="certainly">certainly</span> <span word="does">does</span> <span word="not">not</span> <span word="occur">occur</span> <span word="along">along</span> <span word="lines">lines</span> <span word="broken">broken</span> <span word="by">by</span> <span word="frequent">frequent</span> <span word="offsets">offsets</span> (<span word="an">an</span> <span word="abrupt">abrupt</span> <span word="bend">bend</span> <span word="in">in</span> <span word="an">an</span> <span word="object">object</span> <span word="by">by</span> <span word="which">which</span> <span word="one">one</span> <span word="part">part</span> <span word="is">is</span> <span word="turned">turned</span> <span word="aside">aside</span> <span word="out">out</span> <span word="of">of</span> <span word="line">line</span>) <span word="or">or</span> <span word="changes">changes</span> <span word="in">in</span> <span word="direction">direction</span>, <span word="as">as</span> <span word="the">the</span> <span word="ridge">ridge</span> <span word="is">is</span>. <span word="Also">Also</span> <span word="it">it</span> <span word="is">is</span> <span word="difficult">difficult</span> <span word="to">to</span> <span word="see">see</span> <span word="how">how</span> <span word="the">the</span> <span word="theory">theory</span> <span word="applies">applies</span> <span word="to">to</span> <span word="the">the</span> <span word="plate">plate</span> <span word="between">between</span> <span word="the">the</span> <span word="Mid">Mid</span>-<span word="Atlantic">Atlantic</span> <span word="Ridge">Ridge</span> <span word="and">and</span> <span word="the">the</span> <span word="ridge">ridge</span> <span word="in">in</span> <span word="the">the</span> <span word="Indian">Indian</span> <span word="Ocean">Ocean</span>. <span word="This">This</span> <span word="plate">plate</span> <span word="is">is</span> <span word="growing">growing</span> <span word="on">on</span> <span word="both">both</span> <span word="sides">sides</span>, <span word="and">and</span> <span word="since">since</span> <span word="there">there</span> <span word="is">is</span> <span word="no">no</span> <span word="intermediate">intermediate</span> <span word="trench">trench</span>, <span word="the">the</span> <span word="two">two</span> <span word="ridges">ridges</span> <span word="must">must</span> <span word="be">be</span> <span word="moving">moving</span> <span word="apart">apart</span>. <span word="It">It</span> <span word="would">would</span> <span word="be">be</span> <span word="odd">odd</span> <span word="if">if</span> <span word="the">the</span> <span word="rising">rising</span> <span word="convection">convection</span> <span word="currents">currents</span> <span word="kept">kept</span> <span word="exact">exact</span> <span word="pace">pace</span> <span word="with">with</span> <span word="them">them</span>. <span word="An">An</span> <span word="alternative">alternative</span> <span word="theory">theory</span> <span word="is">is</span> <span word="that">that</span> <span word="the">the</span> <span word="sinking">sinking</span> <span word="part">part</span> <span word="of">of</span> <span word="the">the</span> <span word="plate">plate</span>, <span word="which">which</span> <span word="is">is</span> <span word="denser">denser</span> <span word="than">than</span> <span word="the">the</span> <span word="hotter">hotter</span> <span word="surrounding">surrounding</span> <span word="mantle">mantle</span>, <span word="pulls">pulls</span> <span word="the">the</span> <span word="rest">rest</span> <span word="of">of</span> <span word="the">the</span> <span word="plate">plate</span> <span word="after">after</span> <span word="it">it</span>. <span word="Again">Again</span> <span word="it">it</span> <span word="is">is</span> <span word="difficult">difficult</span> <span word="to">to</span> <span word="see">see</span> <span word="how">how</span> <span word="this">this</span> <span word="applies">applies</span> <span word="to">to</span> <span word="the">the</span> <span word="ridge">ridge</span> <span word="in">in</span> <span word="the">the</span> <span word="South">South</span> <span word="Atlantic">Atlantic</span>, <span word="where">where</span> <span word="neither">neither</span> <span word="the">the</span> <span word="African">African</span> <span word="nor">nor</span> <span word="the">the</span> <span word="American">American</span> <span word="plate">plate</span> <span word="has">has</span> <span word="a">a</span> <span word="sinking">sinking</span> <span word="part">part</span>.</p>
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