2015年3月19日北美GRE考试高频阅读题目
<p>考试吧整理“2015年3月19日北美<span word="GRE">GRE</span>考试高频阅读题目”更多<span word="GRE">GRE</span>阅读、<span word="GRE">GRE</span>精选试题等，请访问考试吧<span word="GRE">GRE</span>考试网！ </p><p> <span word="Although">Although</span>, <span word="recent">recent</span> <span word="years">years</span> <span word="have">have</span> <span word="seen">seen</span> <span word="substantial">substantial</span> <span word="reductions">reductions</span> <span word="in">in</span> <span word="noxious">noxious</span> <span word="pollutants">pollutants</span> <span word="from">from</span> <span word="individual">individual</span> <span word="motor">motor</span> <span word="vehicles">vehicles</span>, <span word="the">the</span> <span word="number">number</span> <span word="of">of</span> <span word="such">such</span> <span word="vehicles">vehicles</span> <span word="has">has</span> <span word="been">been</span> <span word="steadily">steadily</span> <span word="increasing">increasing</span>, <span word="consequently">consequently</span>, <span word="more">more</span> <span word="than">than</span> 100 <span word="cities">cities</span> <span word="in">in</span> <span word="the">the</span> <span word="United">United</span> <span word="States">States</span> <span word="still">still</span> <span word="have">have</span> <span word="levels">levels</span> <span word="of">of</span> <span word="carbon">carbon</span> <span word="monoxide">monoxide</span>, <span word="particulate">particulate</span> <span word="matter">matter</span>, <span word="and">and</span> <span word="ozone">ozone</span> (<span word="generated">generated</span> <span word="by">by</span> <span word="photochemical">photochemical</span> <span word="reactions">reactions</span> <span word="with">with</span> <span word="hydrocarbons">hydrocarbons</span> <span word="from">from</span> <span word="vehicle">vehicle</span> <span word="exhaust">exhaust</span>) <span word="that">that</span> <span word="exceed">exceed</span> <span word="legally">legally</span> <span word="established">established</span> <span word="limits">limits</span>. <span word="There">There</span> <span word="is">is</span> <span word="a">a</span> <span word="growing">growing</span> <span word="realization">realization</span> <span word="that">that</span> <span word="the">the</span> <span word="only">only</span> <span word="effective">effective</span> <span word="way">way</span> <span word="to">to</span> <span word="achieve">achieve</span> <span word="further">further</span> <span word="reductions">reductions</span> <span word="in">in</span> <span word="vehicle">vehicle</span> <span word="emissions">emissions</span>—<span word="short">short</span> <span word="of">of</span> <span word="a">a</span> <span word="massive">massive</span> <span word="shift">shift</span> <span word="away">away</span> <span word="from">from</span> <span word="the">the</span> <span word="private">private</span> <span word="automobile">automobile</span>—<span word="is">is</span> <span word="to">to</span> <span word="replace">replace</span> <span word="conventional">conventional</span> <span word="diesel">diesel</span> <span word="fuel">fuel</span> <span word="and">and</span> <span word="gasoline">gasoline</span> <span word="with">with</span> <span word="cleaner">cleaner</span>-<span word="burning">burning</span> <span word="fuels">fuels</span> <span word="such">such</span> <span word="as">as</span> <span word="compressed">compressed</span> <span word="natural">natural</span> <span word="gas">gas</span>, <span word="liquefied">liquefied</span> <span word="petroleum">petroleum</span> <span word="gas">gas</span>, <span word="ethanol">ethanol</span>, <span word="or">or</span> <span word="methanol">methanol</span>.</p><p> <span word="All">All</span> <span word="of">of</span> <span word="these">these</span> <span word="alternatives">alternatives</span> <span word="are">are</span> <span word="carbon">carbon</span>-<span word="based">based</span> <span word="fuels">fuels</span> <span word="whose">whose</span> <span word="molecules">molecules</span> <span word="are">are</span> <span word="smaller">smaller</span> <span word="and">and</span> <span word="simpler">simpler</span> <span word="than">than</span> <span word="those">those</span> <span word="of">of</span> <span word="gasoline">gasoline</span>. <span word="These">These</span> <span word="molecules">molecules</span> <span word="burn">burn</span> <span word="more">more</span> <span word="cleanly">cleanly</span> <span word="than">than</span> <span word="gasoline">gasoline</span>, <span word="in">in</span> <span word="part">part</span> <span word="because">because</span> <span word="they">they</span> <span word="have">have</span> <span word="fewer">fewer</span>, <span word="if">if</span> <span word="any">any</span>, <span word="carbon">carbon</span>-<span word="carbon">carbon</span> <span word="bonds">bonds</span>, <span word="and">and</span> <span word="the">the</span> <span word="hydrocarbons">hydrocarbons</span> <span word="they">they</span> <span word="do">do</span> <span word="emit">emit</span> <span word="are">are</span> <span word="less">less</span> <span word="likely">likely</span> <span word="to">to</span> <span word="generate">generate</span> <span word="ozone">ozone</span>. <span word="The">The</span> <span word="combustion">combustion</span> <span word="of">of</span> <span word="larger">larger</span> <span word="molecules">molecules</span>, <span word="which">which</span> <span word="have">have</span> <span word="multiple">multiple</span> <span word="carbon">carbon</span>-<span word="carbon">carbon</span> <span word="bonds">bonds</span>, <span word="involves">involves</span> <span word="a">a</span> <span word="more">more</span> <span word="complex">complex</span> <span word="series">series</span> <span word="of">of</span> <span word="reactions">reactions</span>. <span word="These">These</span> <span word="reactions">reactions</span> <span word="increase">increase</span> <span word="the">the</span> <span word="probability">probability</span> <span word="of">of</span> <span word="incomplete">incomplete</span> <span word="combustion">combustion</span> <span word="and">and</span> <span word="are">are</span> <span word="more">more</span> <span word="likely">likely</span> <span word="to">to</span> <span word="release">release</span> <span word="uncombusted">uncombusted</span> <span word="and">and</span> <span word="photochemically">photochemically</span> <span word="active">active</span> <span word="hydrocarbon">hydrocarbon</span> <span word="compounds">compounds</span> <span word="into">into</span> <span word="the">the</span> <span word="atmosphere">atmosphere</span>. <span word="On">On</span> <span word="the">the</span> <span word="other">other</span> <span word="hand">hand</span>, <span word="alternative">alternative</span> <span word="fuels">fuels</span> <span word="do">do</span> <span word="have">have</span> <span word="drawbacks">drawbacks</span>. <span word="Compressed">Compressed</span> <span word="natural">natural</span> <span word="gas">gas</span> <span word="would">would</span> <span word="require">require</span> <span word="that">that</span> <span word="vehicles">vehicles</span> <span word="have">have</span> <span word="a">a</span> <span word="set">set</span> <span word="of">of</span> <span word="heavy">heavy</span> <span word="fuel">fuel</span> <span word="tanks">tanks</span>—<span word="a">a</span> <span word="serious">serious</span> <span word="liability">liability</span> <span word="in">in</span> <span word="terms">terms</span> <span word="of">of</span> <span word="performance">performance</span> <span word="and">and</span> <span word="fuel">fuel</span> <span word="efficiency">efficiency</span>—<span word="and">and</span> <span word="liquefied">liquefied</span> <span word="petroleum">petroleum</span> <span word="gas">gas</span> <span word="faces">faces</span> <span word="fundamental">fundamental</span> <span word="limits">limits</span> <span word="on">on</span> <span word="supply">supply</span>.</p>
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