Practice 3　　Energy-saving vehicles were part of the Green Transportation Festival in the US in 2003. The vehicles shown were designed to reduce America’s dependence on oil and help the environment.　　There are exhibits of cars and buses at the festivals. Most of them use little gas or use another kind of fuel such as natural gas. People are also urged to consider simpler ways of getting around, such as walking, biking and using public transportation systems.　　The United States has less than five per cent of the world’s population, but uses about twenty-five per cent of the world’s oil. More than half of the nation’s oil is imported. Most of it goes to transportation.　　Festival organizers said progress in technology was making it possible for Americans to reduce their dependence on oil. That is because the kinds of energy-saving vehicles are increasing. Efforts to reduce oil imports in the United States would also have important environmental benefits. The burning of oil as fuel is responsible for gases blamed for climate change. When gasoline is burned in cars, it also pollutes the air. This leads to many health problems.