中国的列车根据速度可分为不同类别，以不同的字母和编号区分。
According to the speed, Chinese trains are divided into different classes, identified (确认) with different letters and numbers.
根据《国际疾病分类-第十版》（2006年更新和修订），视力的好坏可分为四个档次
There are four levels of visual function, according to the International Classification of Diseases -10 (Update and Revision 2006)
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