以下结构，属于眼球的屈光系统的是( )

单项选择题当使用魔棒工具选择图像时，在“容差”数值输入框中，输入的数值是下列哪一个所选择的范围相对最大（）。

A.5
B.25
C.10
D.15

单项选择题From this passage we can learn that（）.

A.e-books are better than ordinary books because the letters are clear
B.e-books are not good for people who find reading difficult
C.e-books allow you to store a library in a small unit
D.sales of e-books are expected to increase rapidly in the future