gre阅读练习每日一篇(三十三)
<p> 掌握了<span word="gre">gre</span>阅读里的长难句，到了实战演习的时候了。<span word="gre">gre</span>阅读练习每日一篇帮助<span word="gre">gre</span>考生循序渐进地进行练习和总结。希望<span word="gre">gre</span>考生在进行<span word="gre">gre</span>阅读练习时，也按着考试时候的时间规定自己的练习，这样才能有效果。</p><p> <span word="Eight">Eight</span> <span word="percent">percent</span> <span word="of">of</span> <span word="the">the</span> <span word="Earths">Earths</span> <span word="crust">crust</span> <span word="is">is</span> <span word="aluminum">aluminum</span>, <span word="and">and</span> <span word="there">there</span> <span word="are">are</span> <span word="hundreds">hundreds</span> <span word="of">of</span> <span word="aluminum">aluminum</span>-<span word="bearing">bearing</span> <span word="minerals">minerals</span> <span word="and">and</span> <span word="vast">vast</span> <span word="quantities">quantities</span> <span word="of">of</span> <span word="the">the</span> <span word="rocks">rocks</span> <span word="that">that</span> <span word="contain">contain</span> <span word="them">them</span>. <span word="The">The</span> <span word="best">best</span> <span word="aluminum">aluminum</span> <span word="ore">ore</span> <span word="is">is</span> <span word="bauxite">bauxite</span>, <span word="defined">defined</span> <span word="as">as</span> <span word="aggregates">aggregates</span> <span word="of">of</span> <span word="aluminous">aluminous</span> <span word="minerals">minerals</span>, <span word="more">more</span> <span word="or">or</span> <span word="less">less</span> <span word="impure">impure</span>, <span word="in">in</span> <span word="which">which</span> <span word="aluminum">aluminum</span> <span word="is">is</span> <span word="present">present</span> <span word="as">as</span> <span word="hydrated">hydrated</span> <span word="oxides">oxides</span>. <span word="Bauxite">Bauxite</span> <span word="is">is</span> <span word="the">the</span> <span word="richest">richest</span> <span word="of">of</span> <span word="all">all</span> <span word="those">those</span> <span word="aluminous">aluminous</span> <span word="rocks">rocks</span> <span word="that">that</span> <span word="occur">occur</span> <span word="in">in</span> <span word="large">large</span> <span word="quantities">quantities</span>, <span word="and">and</span> <span word="it">it</span> <span word="yields">yields</span> <span word="alumina">alumina</span>, <span word="the">the</span> <span word="intermediate">intermediate</span> <span word="product">product</span> <span word="required">required</span> <span word="for">for</span> <span word="the">the</span> <span word="production">production</span> <span word="of">of</span> <span word="aluminum">aluminum</span>. <span word="Alumina">Alumina</span> <span word="also">also</span> <span word="occurs">occurs</span> <span word="naturally">naturally</span> <span word="as">as</span> <span word="the">the</span> <span word="mineral">mineral</span> <span word="corundum">corundum</span>, <span word="but">but</span> <span word="corundum">corundum</span> <span word="is">is</span> <span word="not">not</span> <span word="found">found</span> <span word="in">in</span> <span word="large">large</span> <span word="deposits">deposits</span> <span word="of">of</span> <span word="high">high</span> <span word="purity">purity</span>, <span word="and">and</span> <span word="therefore">therefore</span> <span word="it">it</span> <span word="is">is</span> <span word="an">an</span> <span word="impractical">impractical</span> <span word="source">source</span> <span word="for">for</span> <span word="making">making</span> <span word="aluminum">aluminum</span>. <span word="Most">Most</span> <span word="of">of</span> <span word="the">the</span> <span word="many">many</span> <span word="abundant">abundant</span> <span word="nonbauxite">nonbauxite</span> <span word="aluminous">aluminous</span> <span word="minerals">minerals</span> <span word="are">are</span> <span word="silicates">silicates</span>, <span word="and">and</span>, <span word="like">like</span> <span word="all">all</span> <span word="silicate">silicate</span> <span word="minerals">minerals</span>, <span word="they">they</span> <span word="are">are</span> <span word="refractory">refractory</span>, <span word="resistant">resistant</span> <span word="to">to</span> <span word="analysis">analysis</span>, <span word="and">and</span> <span word="extremely">extremely</span> <span word="difficult">difficult</span> <span word="to">to</span> <span word="process">process</span>. <span word="The">The</span> <span word="aluminum">aluminum</span> <span word="silicates">silicates</span> <span word="are">are</span> <span word="therefore">therefore</span> <span word="generally">generally</span> <span word="unsuitable">unsuitable</span> <span word="alternatives">alternatives</span> <span word="to">to</span> <span word="bauxite">bauxite</span> <span word="because">because</span> <span word="considerably">considerably</span> <span word="more">more</span> <span word="energy">energy</span> <span word="is">is</span> <span word="required">required</span> <span word="to">to</span> <span word="extract">extract</span> <span word="alumina">alumina</span> <span word="from">from</span> <span word="them">them</span>.</p><p> 17. <span word="The">The</span> <span word="author">author</span> <span word="implies">implies</span> <span word="that">that</span> <span word="a">a</span> <span word="mineral">mineral</span> <span word="must">must</span> <span word="either">either</span> <span word="be">be</span> <span word="or">or</span> <span word="readily">readily</span> <span word="supply">supply</span> <span word="which">which</span> <span word="of">of</span> <span word="the">the</span> <span word="following">following</span> <span word="in">in</span> <span word="order">order</span> <span word="to">to</span> <span word="be">be</span> <span word="classified">classified</span> <span word="as">as</span> <span word="an">an</span> <span word="aluminum">aluminum</span> <span word="ore">ore</span>?</p><p> <span word="An">An</span> <span word="aggregate">aggregate</span></p>
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