【单选题】
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①
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②
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③
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④
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【单选题】
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①
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②
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③
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④
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【单选题】
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①
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②
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④
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【单选题】
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①
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②
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③
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④
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【单选题】
利用二元关系R的关系图求其对称闭包时,()
②
若两个结点间有一条单向边,则添加一条与其方向相反的边
④
若两个结点间没有边相连,则加上两条方向相反的边
【单选题】
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①
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②
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③
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④
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【单选题】
Q为有理数集,Q上定义运算*为a*b=a+b-ab,则<Q,*>的幺元为()
【单选题】
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①
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②
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③
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④
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