大学英语四六级考试阅读提高的练习（19）
<p> <span word="Plastics">Plastics</span> <span word="are">are</span> <span word="materials">materials</span> <span word="which">which</span> <span word="are">are</span> <span word="softened">softened</span> <span word="by">by</span> <span word="heat">heat</span> <span word="and">and</span> <span word="set">set</span> <span word="into">into</span> <span word="lasting">lasting</span> <span word="form">form</span> <span word="when">when</span> <span word="shaped">shaped</span> <span word="in">in</span> <span word="a">a</span> <span word="mold">mold</span>. <span word="Some">Some</span> <span word="are">are</span> <span word="natural">natural</span>; <span word="some">some</span> <span word="are">are</span> <span word="semi">semi</span>-<span word="synthetic">synthetic</span> , <span word="the">the</span> <span word="result">result</span> <span word="of">of</span> <span word="chemical">chemical</span> <span word="action">action</span> <span word="on">on</span> <span word="natural">natural</span> <span word="substance">substance</span>; <span word="some">some</span> <span word="are">are</span> <span word="synthetic">synthetic</span>, <span word="built">built</span> <span word="up">up</span> <span word="from">from</span> <span word="the">the</span> <span word="constituents">constituents</span> <span word="of">of</span> <span word="oil">oil</span> <span word="or">or</span> <span word="coal">coal</span>. <span word="All">All</span> <span word="are">are</span> <span word="based">based</span> <span word="on">on</span> <span word="the">the</span> <span word="chemistry">chemistry</span> <span word="of">of</span> <span word="carbon">carbon</span>, <span word="with">with</span> <span word="its">its</span> <span word="capacity">capacity</span> <span word="for">for</span> <span word="forming">forming</span> <span word="chains">chains</span>. <span word="The">The</span> <span word="molecules">molecules</span> <span word="that">that</span> <span word="compose">compose</span> <span word="them">them</span> <span word="link">link</span> <span word="together">together</span> <span word="in">in</span> <span word="the">the</span> <span word="setting">setting</span> <span word="or">or</span> <span word="curing">curing</span>(硫化) <span word="process">process</span> <span word="to">to</span> <span word="form">form</span> <span word="chains">chains</span> , <span word="which">which</span> <span word="give">give</span> <span word="plastics">plastics</span> <span word="their">their</span> <span word="flexible">flexible</span> <span word="strength">strength</span>. <span word="Some">Some</span> <span word="plastics">plastics</span> <span word="retain">retain</span> <span word="their">their</span> <span word="ability">ability</span> <span word="to">to</span> <span word="be">be</span> <span word="softened">softened</span> <span word="and">and</span> <span word="reshaped">reshaped</span>; <span word="like">like</span> <span word="wax">wax</span>, <span word="they">they</span> <span word="are">are</span> <span word="thermoplastic">thermoplastic</span>. <span word="Others">Others</span> <span word="set">set</span> <span word="permanently">permanently</span> <span word="in">in</span> <span word="the">the</span> <span word="shapes">shapes</span> <span word="they">they</span> <span word="are">are</span> <span word="given">given</span> <span word="by">by</span> <span word="heat">heat</span> <span word="and">and</span> <span word="pressure">pressure</span>; <span word="like">like</span> <span word="eggs">eggs</span>, <span word="they">they</span> <span word="are">are</span> <span word="thermosetting">thermosetting</span>.</p><p> <span word="From">From</span> <span word="industrial">industrial</span> <span word="beginnings">beginnings</span> <span word="in">in</span> <span word="the">the</span> <span word="nineteenth">nineteenth</span> <span word="century">century</span>, <span word="plastics">plastics</span> <span word="have">have</span> <span word="struggled">struggled</span> <span word="through">through</span> <span word="a">a</span> <span word="hundred">hundred</span> <span word="and">and</span> <span word="twenty">twenty</span> <span word="years">years</span> <span word="of">of</span> <span word="glory">glory</span>, <span word="failure">failure</span>, <span word="disrepute">disrepute</span> <span word="and">and</span> <span word="suspicion">suspicion</span> <span word="on">on</span> <span word="the">the</span> <span word="slow">slow</span> <span word="road">road</span> <span word="to">to</span> <span word="public">public</span> <span word="acceptance">acceptance</span>. <span word="Now">Now</span>, <span word="at">at</span> <span word="last">last</span>, <span word="one">one</span> <span word="can">can</span> <span word="positively">positively</span> <span word="say">say</span> <span word="that">that</span> <span word="plastics">plastics</span> <span word="are">are</span> <span word="appreciated">appreciated</span> <span word="and">and</span> <span word="enjoyed">enjoyed</span> <span word="for">for</span> <span word="what">what</span> <span word="they">they</span> <span word="are">are</span>; <span word="that">that</span> <span word="they">they</span> <span word="make">make</span> <span word="modern">modern</span> <span word="life">life</span> <span word="richer">richer</span>, <span word="more">more</span> <span word="comfortable">comfortable</span> <span word="and">and</span> <span word="convenient">convenient</span>, <span word="and">and</span> <span word="also">also</span> <span word="more">more</span> <span word="fun">fun</span>. <span word="Plastics">Plastics</span> <span word="are">are</span> <span word="warm">warm</span> <span word="materials">materials</span>, <span word="sympathetic">sympathetic</span> <span word="to">to</span> <span word="the">the</span> <span word="human">human</span> <span word="touch">touch</span>, <span word="and">and</span> <span word="their">their</span> <span word="transformation">transformation</span> <span word="into">into</span> <span word="things">things</span> <span word="that">that</span> <span word="come">come</span> <span word="into">into</span> <span word="contact">contact</span> <span word="with">with</span> <span word="human">human</span> <span word="beings">beings</span> <span word="is">is</span> <span word="entirely">entirely</span> <span word="appropriate">appropriate</span>.</p><p> <span word="The">The</span> <span word="fact">fact</span> <span word="that">that</span> <span word="there">there</span> <span word="are">are</span> <span word="plastic">plastic</span> <span word="antiques">antiques</span> <span word="comes">comes</span> <span word="as">as</span> <span word="a">a</span> <span word="shock">shock</span> <span word="to">to</span> <span word="most">most</span> <span word="people">people</span>. <span word="How">How</span> <span word="can">can</span> <span word="a">a</span> <span word="material">material</span> <span word="that">that</span> <span word="seems">seems</span> <span word="so">so</span> <span word="essentially">essentially</span> <span word="twentieth">twentieth</span> <span word="century">century</span>, <span word="and">and</span> <span word="one">one</span> <span word="that">that</span> <span word="is">is</span> <span word="so">so</span> <span word="much">much</span> <span word="associated">associated</span> <span word="with">with</span> <span word="cheap">cheap</span>, <span word="disposable">disposable</span> <span word="products">products</span>, <span word="has">has</span> <span word="a">a</span> <span word="history">history</span> <span word="at">at</span> <span word="all">all</span>? <span word="It">It</span> <span word="is">is</span> <span word="a">a</span> <span word="young">young</span> <span word="technology">technology</span>, <span word="and">and</span> <span word="a">a</span> <span word="great">great</span> <span word="part">part</span> <span word="of">of</span> <span word="the">the</span> <span word="fun">fun</span> <span word="of">of</span> <span word="collecting">collecting</span> <span word="plastics">plastics</span> <span word="is">is</span> <span word="that">that</span> <span word="beautiful">beautiful</span> <span word="pieces">pieces</span> <span word="of">of</span> <span word="historical">historical</span> <span word="interest">interest</span> <span word="can">can</span> <span word="still">still</span> <span word="be">be</span> <span word="found">found</span> <span word="very">very</span> <span word="cheaply">cheaply</span>.</p>
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