We need energy to live and work. Our major source of energy is oil. Oil is one kind of fossil fuel. The amount ot fossil fuels in the world is limited. Therefore, we must save it, and at the same time, we must find new sources of energy. Geothermal heat and nuclear power are alternative sources of energy. They can give us electricity. Other alternative sources are the sun, waves and water. These sources are not only unlimited and available but also clean and safe for the environment. People should develop and use them more and more in the future.