category of a closed subset

例句：

1. 1. The book has several categories of information.
   这本书有多个信息类别。
2. 2. Different categories of animals live in different habitats.
   不同种类的动物生活在不同的栖息地。
3. 3. This category of products is not available in our store.
   这个产品类别在我们的商店里找不到。