六级冲刺练习：阅读（139）
<p> <span word="Today">Today</span> <span word="over">over</span> <span word="ninety">ninety</span>-<span word="eight">eight</span> <span word="per">per</span> <span word="cent">cent</span> <span word="of">of</span> <span word="our">our</span> <span word="energy">energy</span> <span word="comes">comes</span> <span word="from">from</span> <span word="fossil">fossil</span> <span word="fuels">fuels</span>; <span word="coal">coal</span>, <span word="oil">oil</span> <span word="and">and</span> <span word="natural">natural</span> <span word="gas">gas</span>. <span word="But">But</span> <span word="coal">coal</span> <span word="and">and</span> <span word="oil">oil</span> <span word="are">are</span> <span word="not">not</span> <span word="only">only</span> <span word="fuels">fuels</span>. <span word="They">They</span> <span word="are">are</span> <span word="also">also</span> <span word="important">important</span> <span word="raw">raw</span> <span word="materials">materials</span> <span word="for">for</span> <span word="our">our</span> <span word="chemical">chemical</span> <span word="industries">industries</span>. <span word="People">People</span> <span word="now">now</span> <span word="think">think</span> <span word="we">we</span> <span word="should">should</span> <span word="limit">limit</span> <span word="their">their</span> <span word="use">use</span> <span word="as">as</span> <span word="fuel">fuel</span>, <span word="otherwise">otherwise</span> <span word="the">the</span> <span word="worlds">worlds</span> <span word="supply">supply</span> <span word="will">will</span> <span word="soon">soon</span> <span word="run">run</span> <span word="out">out</span>. <span word="Consequently">Consequently</span>, <span word="much">much</span> <span word="research">research</span> <span word="is">is</span> <span word="being">being</span> <span word="done">done</span> <span word="into">into</span> <span word="the">the</span> <span word="practical">practical</span> <span word="use">use</span> <span word="of">of</span> <span word="the">the</span> <span word="sun">sun</span> <span word="for">for</span> <span word="heating">heating</span> <span word="buildings">buildings</span>. <span word="The">The</span> <span word="less">less</span> <span word="fossil">fossil</span> <span word="fuel">fuel</span> <span word="we">we</span> <span word="use">use</span> <span word="now">now</span>, <span word="the">the</span> <span word="more">more</span> <span word="we">we</span> <span word="will">will</span> <span word="have">have</span> <span word="for">for</span> <span word="the">the</span> <span word="future">future</span>.</p><p> <span word="Solar">Solar</span> <span word="energy">energy</span> <span word="is">is</span> <span word="transmitted">transmitted</span> <span word="from">from</span> <span word="the">the</span> <span word="sunthrough">sunthrough</span> <span word="spaceto">spaceto</span> <span word="earth">earth</span> <span word="by">by</span> <span word="electromagnetic">electromagnetic</span> <span word="radiation">radiation</span>. <span word="It">It</span> <span word="must">must</span> <span word="be">be</span> <span word="converted">converted</span> <span word="to">to</span> <span word="heat">heat</span> <span word="before">before</span> <span word="it">it</span> <span word="can">can</span> <span word="be">be</span> <span word="used">used</span>. <span word="Various">Various</span> <span word="types">types</span> <span word="of">of</span> <span word="solar">solar</span> <span word="energy">energy</span> <span word="collectors">collectors</span> <span word="are">are</span> <span word="used">used</span> <span word="to">to</span> <span word="convert">convert</span> <span word="the">the</span> <span word="suns">suns</span> <span word="radiation">radiation</span> <span word="to">to</span> <span word="heat">heat</span>. <span word="Solar">Solar</span>-<span word="heated">heated</span> <span word="hot">hot</span> <span word="water">water</span> <span word="provides">provides</span> <span word="not">not</span> <span word="only">only</span> <span word="the">the</span> <span word="buildings">buildings</span> <span word="hot">hot</span>-<span word="water">water</span> <span word="requirements">requirements</span>, <span word="but">but</span> <span word="space">space</span>-<span word="heating">heating</span> <span word="as">as</span> <span word="well">well</span>. <span word="This">This</span> <span word="solar">solar</span> <span word="system">system</span>, <span word="based">based</span> <span word="on">on</span> <span word="water">water</span>-<span word="heating">heating</span>, <span word="works">works</span> <span word="like">like</span> <span word="this">this</span>. <span word="Each">Each</span> <span word="of">of</span> <span word="its">its</span> <span word="collectors">collectors</span>, <span word="placed">placed</span> <span word="on">on</span> <span word="the">the</span> <span word="roof">roof</span>, <span word="consists">consists</span> <span word="of">of</span> <span word="a">a</span> <span word="shallow">shallow</span> <span word="fiberglass">fiberglass</span> <span word="tray">tray</span> <span word="that">that</span> <span word="holds">holds</span> <span word="a">a</span> <span word="number">number</span> <span word="of">of</span> <span word="copper">copper</span> <span word="tubes">tubes</span> <span word="under">under</span> <span word="a">a</span> <span word="special">special</span> <span word="glass">glass</span> <span word="cover">cover</span>. <span word="The">The</span> <span word="tubes">tubes</span> <span word="are">are</span>, <span word="in">in</span> <span word="turn">turn</span>, <span word="fixed">fixed</span> <span word="to">to</span> <span word="a">a</span> <span word="blackened">blackened</span> <span word="metal">metal</span> <span word="surface">surface</span> <span word="which">which</span> <span word="absorbs">absorbs</span> <span word="energy">energy</span> <span word="from">from</span> <span word="the">the</span> <span word="sun">sun</span>. <span word="The">The</span> <span word="suns">suns</span> <span word="rays">rays</span>, <span word="passing">passing</span> <span word="through">through</span> <span word="the">the</span> <span word="glass">glass</span>, <span word="heat">heat</span> <span word="the">the</span> <span word="water">water</span> <span word="in">in</span> <span word="the">the</span> <span word="tubes">tubes</span>.</p><p> <span word="Since">Since</span> <span word="the">the</span> <span word="energy">energy</span> <span word="is">is</span> <span word="available">available</span> <span word="only">only</span> <span word="during">during</span> <span word="the">the</span> <span word="day">day</span> <span word="and">and</span> <span word="only">only</span> <span word="then">then</span> <span word="when">when</span> <span word="there">there</span> <span word="is">is</span> <span word="not">not</span> <span word="a">a</span> <span word="great">great</span> <span word="deal">deal</span> <span word="of">of</span> <span word="cloud">cloud</span> <span word="cover">cover</span>, <span word="the">the</span> <span word="heat">heat</span> <span word="must">must</span> <span word="be">be</span> <span word="stored">stored</span>. <span word="This">This</span> <span word="can">can</span> <span word="be">be</span> <span word="done">done</span> <span word="in">in</span> <span word="water">water</span>, <span word="or">or</span> <span word="in">in</span> <span word="rock">rock</span> <span word="or">or</span> <span word="pebble">pebble</span> <span word="beds">beds</span>. <span word="The">The</span> <span word="energy">energy</span> <span word="is">is</span> <span word="stored">stored</span> <span word="in">in</span> <span word="the">the</span> <span word="hot">hot</span> <span word="water">water</span> <span word="in">in</span> <span word="the">the</span> <span word="pipes">pipes</span>.</p><p> 21. <span word="Solar">Solar</span> <span word="energy">energy</span> <span word="was">was</span> <span word="first">first</span> <span word="used">used</span>_______.</p>
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