大学英语六级考试阅读提高练习题及答案(11)
<p> <span word="For">For</span> <span word="as">as</span> <span word="long">long</span> <span word="as">as</span> <span word="humans">humans</span> <span word="have">have</span> <span word="raised">raised</span> <span word="crops">crops</span> <span word="as">as</span> <span word="a">a</span> <span word="source">source</span> <span word="of">of</span> <span word="food">food</span> <span word="and">and</span> <span word="other">other</span> <span word="products">products</span>, <span word="insects">insects</span> <span word="have">have</span> <span word="damaged">damaged</span> <span word="them">them</span>. <span word="Between">Between</span> 1870 <span word="and">and</span> 1880, <span word="locusts">locusts</span> <span word="ate">ate</span> <span word="millions">millions</span> <span word="of">of</span> <span word="dollars">dollars</span> <span word="worth">worth</span> <span word="of">of</span> <span word="crops">crops</span> <span word="in">in</span> <span word="the">the</span> <span word="Mississippi">Mississippi</span> <span word="Valley">Valley</span>. <span word="Today">Today</span> <span word="in">in</span> <span word="the">the</span> <span word="United">United</span> <span word="States">States</span> <span word="the">the</span> <span word="cotton">cotton</span> <span word="boll">boll</span> <span word="weevil">weevil</span> <span word="damages">damages</span> <span word="about">about</span> 300 <span word="million">million</span> <span word="dollars">dollars</span> <span word="worth">worth</span> <span word="of">of</span> <span word="crops">crops</span> <span word="each">each</span> <span word="year">year</span>. <span word="Additional">Additional</span> <span word="millions">millions</span> <span word="are">are</span> <span word="lost">lost</span> <span word="each">each</span> <span word="year">year</span> <span word="to">to</span> <span word="the">the</span> <span word="appetites">appetites</span> <span word="of">of</span> <span word="other">other</span> <span word="plant">plant</span>-<span word="eating">eating</span> <span word="insects">insects</span>. <span word="Some">Some</span> <span word="of">of</span> <span word="these">these</span> <span word="are">are</span> <span word="corn">corn</span> <span word="borers">borers</span>, <span word="gypsy">gypsy</span> <span word="moths">moths</span>, <span word="potato">potato</span> <span word="beetles">beetles</span>, <span word="and">and</span> <span word="Japanese">Japanese</span> <span word="beetles">beetles</span>.</p><p> <span word="In">In</span> <span word="modern">modern</span> <span word="times">times</span>, <span word="many">many</span> <span word="powerful">powerful</span> <span word="insecticides">insecticides</span> <span word="have">have</span> <span word="been">been</span> <span word="used">used</span> <span word="in">in</span> <span word="an">an</span> <span word="attempt">attempt</span> <span word="to">to</span> <span word="destroy">destroy</span> <span word="insects">insects</span> <span word="that">that</span> <span word="damage">damage</span> <span word="crops">crops</span> <span word="and">and</span> <span word="trees">trees</span>. <span word="Some">Some</span> <span word="kinds">kinds</span> <span word="of">of</span> <span word="insecticides">insecticides</span>, <span word="when">when</span> <span word="carefully">carefully</span> <span word="used">used</span>, <span word="have">have</span> <span word="worked">worked</span> <span word="well">well</span>. <span word="Yet">Yet</span> <span word="the">the</span> <span word="same">same</span> <span word="insecticides">insecticides</span> <span word="have">have</span> <span word="caused">caused</span> <span word="some">some</span> <span word="unexpected">unexpected</span> <span word="problems">problems</span>. <span word="In">In</span> <span word="one">one</span> <span word="large">large</span> <span word="area">area</span>, <span word="an">an</span> <span word="insecticide">insecticide</span> <span word="was">was</span> <span word="used">used</span> <span word="against">against</span> <span word="Japanese">Japanese</span> <span word="beetles">beetles</span>, <span word="which">which</span> <span word="eat">eat</span> <span word="almost">almost</span> <span word="any">any</span> <span word="kind">kind</span> <span word="of">of</span> <span word="flower">flower</span> <span word="or">or</span> <span word="leaf">leaf</span>. <span word="Shortly">Shortly</span> <span word="afterward">afterward</span>, <span word="the">the</span> <span word="number">number</span> <span word="of">of</span> <span word="corn">corn</span> <span word="borers">borers</span> <span word="almost">almost</span> <span word="doubled">doubled</span>. <span word="As">As</span> <span word="intended">intended</span>, <span word="the">the</span> <span word="insecticide">insecticide</span> <span word="had">had</span> <span word="killed">killed</span> <span word="many">many</span> <span word="Japanese">Japanese</span> <span word="beetles">beetles</span>. <span word="But">But</span> <span word="it">it</span> <span word="had">had</span> <span word="killed">killed</span> <span word="many">many</span> <span word="of">of</span> <span word="the">the</span> <span word="insect">insect</span> <span word="enemies">enemies</span> <span word="of">of</span> <span word="the">the</span> <span word="corn">corn</span> <span word="borer">borer</span> <span word="as">as</span> <span word="well">well</span>.</p><p> <span word="In">In</span> <span word="another">another</span> <span word="case">case</span>, <span word="an">an</span> <span word="insecticide">insecticide</span> <span word="was">was</span> <span word="used">used</span> <span word="in">in</span> <span word="Louisiana">Louisiana</span> <span word="to">to</span> <span word="kill">kill</span> <span word="the">the</span> <span word="troublesome">troublesome</span> <span word="fire">fire</span> <span word="ant">ant</span>. <span word="The">The</span> <span word="insecticide">insecticide</span> <span word="did">did</span> <span word="not">not</span> <span word="kill">kill</span> <span word="many">many</span> <span word="fire">fire</span> <span word="ants">ants</span>. <span word="It">It</span> <span word="did">did</span> <span word="kill">kill</span> <span word="several">several</span> <span word="small">small</span> <span word="animals">animals</span>. <span word="It">It</span> <span word="also">also</span> <span word="killed">killed</span> <span word="some">some</span> <span word="insect">insect</span> <span word="enemies">enemies</span> <span word="of">of</span> <span word="the">the</span> <span word="sugarcane">sugarcane</span> <span word="borer">borer</span>, <span word="a">a</span> <span word="much">much</span> <span word="more">more</span> <span word="destructive">destructive</span> <span word="pest">pest</span> <span word="than">than</span> <span word="the">the</span> <span word="fire">fire</span> <span word="ants">ants</span>. <span word="As">As</span> <span word="a">a</span> <span word="result">result</span>, <span word="the">the</span> <span word="number">number</span> <span word="of">of</span> <span word="sugarcane">sugarcane</span> <span word="borers">borers</span> <span word="increased">increased</span> <span word="and">and</span> <span word="severely">severely</span> <span word="damaged">damaged</span> <span word="the">the</span> <span word="sugarcane">sugarcane</span> <span word="crop">crop</span>.</p><p> <span word="To">To</span> <span word="be">be</span> <span word="sure">sure</span> <span word="that">that</span> <span word="one">one</span> <span word="insect">insect</span> <span word="pest">pest</span> <span word="will">will</span> <span word="not">not</span> <span word="be">be</span> <span word="traded">traded</span> <span word="for">for</span> <span word="another">another</span> <span word="when">when</span> <span word="an">an</span> <span word="insecticide">insecticide</span> <span word="is">is</span> <span word="used">used</span>, <span word="scientists">scientists</span> <span word="must">must</span> <span word="perform">perform</span> <span word="careful">careful</span> <span word="experiments">experiments</span> <span word="and">and</span> <span word="do">do</span> <span word="wide">wide</span> <span word="research">research</span>. <span word="The">The</span> <span word="experiments">experiments</span> <span word="and">and</span> <span word="research">research</span> <span word="provide">provide</span> <span word="knowledge">knowledge</span> <span word="of">of</span> <span word="the">the</span> <span word="possible">possible</span> <span word="hazards">hazards</span> <span word="an">an</span> <span word="insecticide">insecticide</span> <span word="may">may</span> <span word="bring">bring</span> <span word="to">to</span> <span word="plant">plant</span> <span word="and">and</span> <span word="animal">animal</span> <span word="communities">communities</span>. <span word="Without">Without</span> <span word="such">such</span> <span word="knowledge">knowledge</span>, <span word="we">we</span> <span word="have">have</span> <span word="found">found</span> <span word="that">that</span> <span word="nature">nature</span> <span word="sometimes">sometimes</span> <span word="responds">responds</span> <span word="to">to</span> <span word="insecticides">insecticides</span> <span word="in">in</span> <span word="unexpected">unexpected</span> <span word="ways">ways</span>.</p>
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