"Everybody in this city wants a car, and I'm no exception. A car brings with it the freedom to travel", said a friend of mine while reading a car magazine. I might not agree with him, but no doubt he was speaking for a rapidly growing number of middle-class Chinese. While it is true that all the waiting, walking, being part of a crowd, and sweating, are somewhat unpleasant, there are many problems which can arise when our lives rely too much on this invention. First of all, in terms of polluting the environment, driving a car is the worst act an average person can _ . Beijing now finds itself at the top of the list of the most polluted capital cities in the world with Mexico City in the second place. Research also shows that by 2010 around 90% of total pollutants in Shanghai have come from cars. These pollutions are extremely dangerous to our health. They can damage the lungs, cause cancer, and damage the brain. Apart from environmental problems, relying too much on cars also creates social problems such as traffic jams, road accidents, and noise pollution. The jeeps that proudly drive through the Hutongs in Beijing as if they are in a race often annoy me, and to make it worse, these drivers seldom respect cyclists. Of course, we cannot forget the convenience that cars bring us when we need to travel far, but I often find it faster to cycle from one place to another within the city of Beijing, especially with the growing traffic jams. Since people travel further and more frequently than before, cars will certainly be important in the future. At the same time, however, let us work hard to make sure that this invention brings us a more convenient lifestyle rather than trouble and disease. Let us make good use of cars. What is this passage mainly about?
Environmental problems. Traffic jams in Beijing. Problems brought about by cars. Benefits of using cars.