Listening Comprehension (Test A)

In most cities, smoke and exhaust fumes from cars and factories pose a threat to people's health. This air pollution, known as smog, is a serious problem. To address it, smoke ordinances have been passed and vehicles and factories are monitored to reduce harmful emissions. Today, in most cities, smoke and exhaust fumes fill the air and endanger the health and well-being of the people. Smoke and exhaust fumes contain harmful by-products from gasoline burned in cars and from factories. Air pollution, or smog, is a serious problem in some cities. Smog consists of smoke and exhaust fumes mixed with fog. To control air pollution, smoke ordinances have been passed. Smoke-belching vehicles are checked and factories are required to reduce fumes emanating from them.