Recently an 1) _________ heavy smog hit the city, making the air 2) _________ to breathe. Air pollution has been a serious problem in the city for years. It is caused by the rapid 3) ____________ growth in the country. Coal-burning energy plants emit harmful gases into the air and millions of 4) _________ in the city add to the pollution. Clean air is very important to people’s 5) __________ of life. Unfortunately, as long as economic growth remains the city’s first priority, it is 6) _________ that a big sea change will take place any time soon.