gre考试阅读真题解析(B)
<p> <span word="One">One</span> <span word="explanation">explanation</span> <span word="for">for</span> <span word="the">the</span> <span word="tendency">tendency</span> <span word="of">of</span> <span word="animals">animals</span> <span word="to">to</span> <span word="be">be</span> <span word="more">more</span> <span word="vigilant">vigilant</span> <span word="in">in</span> <span word="smaller">smaller</span> <span word="groups">groups</span> <span word="than">than</span> <span word="in">in</span> <span word="larger">larger</span> <span word="ones">ones</span> <span word="assumes">assumes</span> <span word="that">that</span> <span word="the">the</span> <span word="vigilant">vigilant</span> <span word="behaviorlooking">behaviorlooking</span> <span word="up">up</span>, <span word="for">for</span> <span word="exampleis">exampleis</span> <span word="aimed">aimed</span> <span word="at">at</span> <span word="predators">predators</span>. <span word="If">If</span> <span word="individuals">individuals</span> <span word="on">on</span> <span word="the">the</span> <span word="edge">edge</span> <span word="of">of</span> <span word="a">a</span> <span word="group">group</span> <span word="are">are</span> <span word="more">more</span> <span word="vigilant">vigilant</span> <span word="because">because</span> <span word="they">they</span> <span word="are">are</span> <span word="at">at</span> <span word="greater">greater</span> <span word="risk">risk</span> <span word="of">of</span> <span word="being">being</span> <span word="captured">captured</span>, <span word="then">then</span> <span word="individuals">individuals</span> <span word="on">on</span> <span word="average">average</span> <span word="would">would</span> <span word="have">have</span> <span word="to">to</span> <span word="be">be</span> <span word="more">more</span> <span word="vigilant">vigilant</span> <span word="in">in</span> <span word="smaller">smaller</span> <span word="groups">groups</span>, <span word="because">because</span> <span word="the">the</span> <span word="animals">animals</span> <span word="on">on</span> <span word="the">the</span> <span word="periphery">periphery</span> <span word="of">of</span> <span word="a">a</span> <span word="group">group</span> <span word="form">form</span> <span word="a">a</span> <span word="greater">greater</span> <span word="proportion">proportion</span> <span word="of">of</span> <span word="the">the</span> <span word="whole">whole</span> <span word="group">group</span> <span word="as">as</span> <span word="the">the</span> <span word="size">size</span> <span word="of">of</span> <span word="the">the</span> <span word="group">group</span> <span word="diminishes">diminishes</span>.</p><p> <span word="However">However</span>, <span word="a">a</span> <span word="different">different</span> <span word="explanation">explanation</span> <span word="is">is</span> <span word="necessary">necessary</span> <span word="in">in</span> <span word="cases">cases</span> <span word="where">where</span> <span word="the">the</span> <span word="vigilant">vigilant</span> <span word="behavior">behavior</span> <span word="is">is</span> <span word="not">not</span> <span word="directed">directed</span> <span word="at">at</span> <span word="predators">predators</span>. <span word="J">J</span>. <span word="Krebs">Krebs</span> <span word="has">has</span> <span word="discovered">discovered</span> <span word="that">that</span> <span word="great">great</span> <span word="blue">blue</span> <span word="herons">herons</span> <span word="look">look</span> <span word="up">up</span> <span word="more">more</span> <span word="often">often</span> <span word="when">when</span> <span word="in">in</span> <span word="smaller">smaller</span> <span word="flocks">flocks</span> <span word="than">than</span> <span word="when">when</span> <span word="in">in</span> <span word="larger">larger</span> <span word="ones">ones</span>, <span word="solely">solely</span> <span word="as">as</span> <span word="a">a</span> <span word="consequence">consequence</span> <span word="of">of</span> <span word="poor">poor</span> <span word="feeding">feeding</span> <span word="conditions">conditions</span>. <span word="Krebs">Krebs</span> <span word="hypothesizes">hypothesizes</span> <span word="that">that</span> <span word="the">the</span> <span word="herons">herons</span> <span word="in">in</span> <span word="smaller">smaller</span> <span word="flocks">flocks</span> <span word="are">are</span> <span word="watching">watching</span> <span word="for">for</span> <span word="herons">herons</span> <span word="that">that</span> <span word="they">they</span> <span word="might">might</span> <span word="follow">follow</span> <span word="to">to</span> <span word="better">better</span> <span word="feeding">feeding</span> <span word="pools">pools</span>, <span word="which">which</span> <span word="usually">usually</span> <span word="attract">attract</span> <span word="larger">larger</span> <span word="numbers">numbers</span> <span word="of">of</span> <span word="the">the</span> <span word="birds">birds</span>.</p><p> 17. <span word="It">It</span> <span word="can">can</span> <span word="be">be</span> <span word="inferred">inferred</span> <span word="from">from</span> <span word="the">the</span> <span word="passage">passage</span> <span word="that">that</span> <span word="in">in</span> <span word="species">species</span> <span word="in">in</span> <span word="which">which</span> <span word="vigilant">vigilant</span> <span word="behavior">behavior</span> <span word="is">is</span> <span word="directed">directed</span> <span word="at">at</span> <span word="predators">predators</span>, <span word="the">the</span> <span word="tendency">tendency</span> <span word="of">of</span> <span word="the">the</span> <span word="animals">animals</span> <span word="to">to</span> <span word="be">be</span> <span word="more">more</span> <span word="vigilant">vigilant</span> <span word="in">in</span> <span word="smaller">smaller</span> <span word="groups">groups</span> <span word="than">than</span> <span word="in">in</span> <span word="larger">larger</span> <span word="ones">ones</span> <span word="would">would</span> <span word="most">most</span> <span word="likely">likely</span> <span word="be">be</span> <span word="minimized">minimized</span> <span word="if">if</span> <span word="which">which</span> <span word="of">of</span> <span word="the">the</span> <span word="following">following</span> <span word="were">were</span> <span word="true">true</span>?</p><p> <span word="The">The</span> <span word="vigilance">vigilance</span> <span word="of">of</span> <span word="animals">animals</span> <span word="on">on</span> <span word="the">the</span> <span word="periphery">periphery</span> <span word="of">of</span> <span word="a">a</span> <span word="group">group</span> <span word="always">always</span> <span word="exceeded">exceeded</span> <span word="that">that</span> <span word="of">of</span> <span word="animals">animals</span> <span word="located">located</span> <span word="in">in</span> <span word="its">its</span> <span word="interior">interior</span>, <span word="even">even</span> <span word="when">when</span> <span word="predators">predators</span> <span word="were">were</span> <span word="not">not</span> <span word="in">in</span> <span word="the">the</span> <span word="area">area</span>.</p><p> <span word="The">The</span> <span word="risk">risk</span> <span word="of">of</span> <span word="capture">capture</span> <span word="for">for</span> <span word="individuals">individuals</span> <span word="in">in</span> <span word="a">a</span> <span word="group">group</span> <span word="was">was</span> <span word="the">the</span> <span word="same">same</span>, <span word="whether">whether</span> <span word="they">they</span> <span word="were">were</span> <span word="located">located</span> <span word="in">in</span> <span word="the">the</span> <span word="interior">interior</span> <span word="of">of</span> <span word="the">the</span> <span word="group">group</span> <span word="or">or</span> <span word="on">on</span> <span word="its">its</span> <span word="periphery">periphery</span>.</p>
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