职称英语《综合类》考试语法讲解：情态动词
<p> <span word="can">can</span> / <span word="may">may</span> / <span word="should">should</span> / <span word="ought">ought</span> <span word="to">to</span> / <span word="must">must</span> / <span word="need">need</span>等动词称为情态动词。情态动词有三大特征：一是无人称和数的变化，二是后面跟的动词不带<span word="to">to</span>，三是后面 + <span word="not">not</span>构成否定式，比较：</p><p> <span word="He">He</span> <span word="neednt">neednt</span> <span word="go">go</span> <span word="there">there</span> <span word="so">so</span> <span word="early">early</span>.</p><p> <span word="You">You</span> <span word="do">do</span> <span word="not">not</span> <span word="need">need</span> <span word="to">to</span> <span word="be">be</span> <span word="an">an</span> <span word="expert">expert</span> <span word="to">to</span> <span word="make">make</span> <span word="this">this</span> <span word="simple">simple</span> <span word="design">design</span>.</p><p> 在讲解情态动词完成式前，先将一般式中应注意的几个问题提一下，以引起必要的重视。</p><p> 1.情态动词一般式中应注意的几个问题：</p><p> 注意以下用法的习惯与区别：</p><p> <span word="He">He</span> <span word="must">must</span> <span word="be">be</span> <span word="a">a</span> <span word="doctor">doctor</span>.</p><p> 否定：<span word="He">He</span> <span word="cant">cant</span> <span word="be">be</span> <span word="a">a</span> <span word="doctor">doctor</span>.</p><p> 又如：<span word="They">They</span> <span word="cant">cant</span> <span word="be">be</span> <span word="working">working</span> <span word="now">now</span>.</p><p> <span word="May">May</span> <span word="I">I</span> <span word="go">go</span> <span word="now">now</span>?</p><p> 回答：<span word="Yes">Yes</span>, <span word="please">please</span>. / <span word="Please">Please</span> <span word="dont">dont</span>.</p><p> <span word="have">have</span> <span word="to">to</span> 与 <span word="must">must</span></p><p> 1) 当强调外界原因时，2) 当与将来时结合时，用<span word="have">have</span> <span word="to">to</span>，</p><p> 例如：</p><p> <span word="Since">Since</span> <span word="it">it</span> <span word="is">is</span> <span word="raining">raining</span>, <span word="we">we</span> <span word="have">have</span> <span word="to">to</span> <span word="sty">sty</span> <span word="indoors">indoors</span>.</p><p> <span word="You">You</span> <span word="will">will</span> <span word="have">have</span> <span word="to">to</span> <span word="hurry">hurry</span> <span word="if">if</span> <span word="you">you</span> <span word="want">want</span> <span word="to">to</span> <span word="catch">catch</span> <span word="the">the</span> 9:30 <span word="train">train</span>.</p><p> 3) 表示自然规律或必然结果，用<span word="must">must</span>，</p><p> 例如：</p><p> <span word="All">All</span> <span word="men">men</span> <span word="must">must</span> <span word="die">die</span>.</p><p> <span word="can">can</span> 与<span word="be">be</span> <span word="able">able</span> <span word="to">to</span></p><p> <span word="can">can</span>表示能力，但不一定做了或做成了;<span word="be">be</span> <span word="able">able</span> <span word="to">to</span> 表示有能力并且做成了，相当于<span word="succeed">succeed</span> <span word="in">in</span> <span word="doing">doing</span>, 例如：</p>
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