1. Books in the library are classified by country, Chinese and foreign languages; There are also times, classical and modern; There are also points by nature, such as science and technology, literature and political economy.

2. There are many kinds of whales, which are generally divided into two categories: one is baleen whales, which have no teeth; One is the toothed whale, which has sharp teeth.

There are two main ways to deal with sandstorm. One can be called guerrilla warfare; One can be called positional warfare. March into the desert.