唐氏综合症是最常见的引发智力缺陷的遗传因素。

Down syndrome is the most common genetic cause of mental retardation.

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他说工厂和一个叫方的男子定有合同，方为砖厂提供并监管有智力缺陷的工人。

He said the factory contracted with a man named Fang who would supply and supervise mentally disabled workers.

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因此，缺碘——这唯一可预防的、导致智力缺陷的疾病——是一个重要的公共健康问题。

Thus iodine deficiency, as the single greatest preventable cause of mental retardation, is an important public-health problem.

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