范围较宽的中间区域包含与您当前所选主题相关的内容，按逻辑分组排列。
The wide center area contains content, arranged in logical groupings, that relate to the topic you currently have selected.
这个练习需要更多技巧，因为要按照分组和周期将数据排列成常见的格式，所以需要某些具有想像力的代码，不能简单地将各部分放在固定的位置。
What about the entire periodic table? That exercise is trickier because you have to arrange the data into the familiar format based on group and period, which requires some fancy coding.
有一年，为了实现精确分组，德格拉卡在自家客厅地板上把标有学员名字及基本概况的索引卡摊了一地，试验了各种排列组合，最终使所有人员得到了均衡的分配。
One year, to get the study groups just-so, Ms. DeGraca laid out index CARDS with students' names and basic facts on her living room floor, mixing and matching until the groups seem balanced.
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