【正确答案】As can be seen from the table, most of the important cities of our country are highly-polluted, especially the big cities such as Beijing, Taiyuan, Chongqing, Lanzhou etc. The API of them reaches as high as above 100. Among the twenty-two cities, only 3 cities are in the first level; the others fall into the second and the third. And the number of most seriously-polluted cities on or above the third level occupies about 1/4 of the total.
As to the serious air pollution, it's time for us to take measures to protect our living environment. On the one hand, we must enlarge the size of green-covered land so as to avoid the sandy wind. On the other hand, we must establish strict laws to reduce waste gases produced by automobiles and punish the factories that emit a large amount of TSP or NO_x and even close some of them. Only in this way could the air of the main cities be cleaned up.