矛盾就在此了：更多的钱不能够产生更高的回报。因为长寿命，识字能力或者健康的身体不能够用钱买到。
The hitch: more money can not yield ever higher returns, because there is only that much longevity, literacy or better health that money can buy.
有语言障碍的孩子可能不认识字母，或者无法将字母与他们的读音相联系。
While learning to read, children with dyslexia may not recognize letters or connect them with their sounds.
一个数据表都有一个或者是若干个列，而每个表都可以有唯一标识列的字段，这些能够标识字段的列就是所谓的主键。
A database table commonly has a column, or group of columns, that uniquely identifies each row in the table. This identifying column or group of columns is called the primary key.
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