近年来高铁酸钾(K₂FeO₄)已经被广泛应用在水处理方面，高铁酸钾的氧化性超过高锰酸钾，是一种集氧化、吸附、凝聚、杀菌的新型高效的多功能水处理剂。高铁酸钾在水处理过程中涉及到的过程正确的有 (  )

①蛋白质的变性  ②蛋白质的盐析

③胶体聚沉  ④盐类水解

⑤焰色反应  ⑥氧化还原反应

下列各组省区中，人口密度最小的是  (  )                                            

News 1
Yuan Longping, the father of hybrid rice, won the World Food Prize on Monday. Yuan developed the world's first popular and widely known hybrid rice. Hybrid rice plants can make more rice than regular ones.
News 2
Have you ever got angry at books that are full of mistakes? Don't worry, things will get better soon. Last week, China started checking textbooks, dictionaries and children's books all over the country. The government said the results of the check would come out at the end of June.
News 3
People will see a new "star" in the sky soon. China plants to send a satellite into space by December 2006.It will stay in space for one year. It will go around the moon and take pictures. It must be very expensive, right? That's for sure,1.4 billion yuan!
News 4
Have you ever thought of being able to fly around the world in a few hours? One day, maybe you can. Last Saturday, the American X-43A airplane made its first flight. It reached a speed of 8,000 kilometers per hour. This makes it the fastest plane in the world.X-43A is only three to four meters long, but it's very heavy. It weighs 1,270 kilograms.

3∶4=120∶160还可以写成 $\frac{3}{4}=\frac{120}{160}$ 。