2017高考英语一轮语法对点讲练：4 情态动词和虚拟语气
<p> 语法对点讲练四 情态动词和虚拟语气</p><p> 一、情态动词</p><p> 知识点讲解</p><p> 情态动词本身有一定的词义，但需和其他动词一起构成谓语。除<span word="have">have</span> <span word="to">to</span>, <span word="be">be</span> <span word="able">able</span> <span word="to">to</span>外，情态动词无人称和数的变化。除<span word="have">have</span> <span word="to">to</span>, <span word="be">be</span> <span word="able">able</span> <span word="to">to</span>外，情态动词只有现在时和过去时两种基本形式。除<span word="ought">ought</span>, <span word="used">used</span>外，情态动词后面接不带<span word="to">to</span>的不定式。情态动词中<span word="have">have</span> <span word="to">to</span>可以用<span word="have">have</span> <span word="got">got</span> <span word="to">to</span>代替；<span word="need">need</span>, <span word="dare">dare</span>也可用作实义动词；<span word="used">used</span> <span word="to">to</span>有两种否定形式：<span word="used">used</span> <span word="not">not</span> <span word="to">to</span>和<span word="did">did</span> <span word="not">not</span> <span word="use">use</span> <span word="to">to</span>。</p><p> 1．<span word="can">can</span>, <span word="could">could</span></p><p> ①表示具有某种能力，指有能力做某事。<span word="could">could</span>表示过去的能力。</p><p> ②表示请求和允许，和<span word="may">may</span>相近；口语中可用<span word="could">could</span>表示委婉语气，但回答时仍用<span word="can">can</span>。</p><p> ③表示可能性，常用于否定句和疑问句中。</p><p> ④表示惊异、怀疑、不相信的态度。</p><p> 特别提示 </p><p> ⑤“<span word="can">can</span> <span word="not">not</span>/<span word="never">never</span> ... <span word="too">too</span>/<span word="enough">enough</span>”表示“无论怎么……也不过分；越……越好”。</p><p> <span word="You">You</span> <span word="can">can</span>'<span word="t">t</span> <span word="be">be</span> <span word="too">too</span> <span word="careful">careful</span> <span word="when">when</span> <span word="travelling">travelling</span> <span word="alone">alone</span>.</p><p> ⑥<span word="cannot">cannot</span> <span word="but">but</span> <span word="do">do</span> <span word="sth">sth</span>.表示“只好；不得不”。</p><p> <span word="Father">Father</span> <span word="cannot">cannot</span> <span word="but">but</span> <span word="agree">agree</span> <span word="with">with</span> <span word="his">his</span> <span word="daughter">daughter</span>'<span word="s">s</span> <span word="opinion">opinion</span>.</p><p> ⑦<span word="can">can</span>'<span word="t">t</span> <span word="help">help</span> <span word="doing">doing</span> <span word="sth">sth</span>.表示“禁不住做某事”。</p><p> 2．<span word="be">be</span> <span word="able">able</span> <span word="to">to</span></p>
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