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Yang Cangxu has recently become hot on the Internet. He is considered as a hero, and known as "A Professional Life Saviour", because he has saved 24 people's lives during the past 26 years. Yang, a typical Chinese farmer, lives in Baoji, Shanxi Province.  He is good at

swimming, which is also his favorite. When he was young, he joined the army.  The life in the army had a great influence on him. It also helped to form one of his characters(性格) --being ready to help others. Just seven to eight meters away from his home flows a channel(水渠). The water is very deep and flows fast. There is a bridge over the channel. Walking across the bridge is not an easy thing. From time to time, people fall into the water. If this happens, the person must be saved in time. Otherwise, he or she will be washed away by the water.

Yang Cangxu is always the first one to rush to the channel to save the drowning (溺水)person. We must learn from him.

小题1:What does Yang Cangxu do ?__________________________________________

小题2:Why is he considered as a hero? __________________________________________

小题3:Does he like swimming best? __________________________________________

有七种物质：①水；②氧气；③二氧化碳；④氮气；⑤氯酸钾；⑥空气；⑦河水；用序号填空，其中属于混合物的是：______，属于纯净物的是______，属于单质的是______，属于化合物的是______．