One report concludes that many schools do not have, or likely to have, enough computers to use them effectively.
or
nor
or are
nor are they
nor are not
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C.中or身后的not不可以省略，因为前后句中的helping verb是不同的，只有前后句helping verb相同，第二个not才可以省略。One report concludes that many schools do not have, or are not likely to have, enough computer to use them efficiently.
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C.中or身后的not不可以省略，因为前后句中的helping verb是不同的，只有前后句helping verb相同，第二个not才可以省略。One report concludes that many schools do not have, or are not likely to have, enough computer to use them efficiently.
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