过去完成时
过去完成时的基本结构
重要程度：8 分
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<h2>过去完成时的基本结构</h2>
<p>过去完成时用来表示在过去某一时间或动作之前已经发生或完成了的动作。它由 <strong>had + 过去分词</strong> 构成。</p>
<h3>肯定句</h3>
<p>主语 + had + 过去分词 + 其他成分</p>
<p><strong>例句：</strong>She had finished her homework before she went to bed.</p>
<h3>否定句</h3>
<p>主语 + had + not (hadn't) + 过去分词 + 其他成分</p>
<p><strong>例句：</strong>He hadn't eaten breakfast when he arrived at the office.</p>
<h3>疑问句</h3>
<p>Had + 主语 + 过去分词 + 其他成分?</p>
<p><strong>例句：</strong>Had they visited the museum before the tour guide arrived?</p>
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