三情态动词
语法精讲情态动词是历年高考英语命题中不可缺少的考察内容。它涉及谈话所说的内容的态度和看法，或者表主观设想及其他情态意义的助动词。正确掌握其用法是解题的关键。其意义与用法如下：
一. 表推测
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对现在的推测
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对过去的推测
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肯定
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否定
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肯定
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否定
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must do
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can’t do
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must have + V-ed
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can’t have + V-ed
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could do
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couldn’t do
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could have + V-ed
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couldn’t have +V-ed
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may do
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may not do
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may have + V-ed
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may not have +V-ed
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might do
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might not do
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might have V-ed
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might not have V-ed
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表推测性用法的含义
may: a) 许可 b)祝愿
can a) 能力 b)许可 c)惊异，怀疑，不相信的态度
must a)必须 b) 必然
ought to a) 应该（义务和责任）
