Search in the search engines question is, is the high frequency of site Q & A class, so in the Q & A class web site outside the chain is necessary.

在搜索引擎中搜问题是，出现频率高的就是问答类的网站，所以在问答类网站获取外链是很有必要的。

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It is interesting to note that the frequency of bronchitis and pneumonia in Great Britain has been correlated with area of residence in a polluted area and with social class.

值得指出的是，在英国， 支气管炎和肺炎的发病率与污染区域中的居住地区和所属社会阶层有关。

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Produces a list of the unique code occurrences and their frequency in an output table for a specified set of fields from an input feature class or table.

对于一个输入元素类或表格中具体指定的一组字段，在一个输出表格中生成一个特定的代码事件及频率列表。

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