Today almost 70% of the electrical power we use comes from power plants that use fossil fuels (矿物燃料) to make electricity. Fossil fuels, such as oil, coal, and natural gas, are burned to make electricity. Burning fossil fuels releases pollution and carbon dioxide gas ( C02 ) into the air. The more fossil fuels we burn, the warmer the air around Earth gets. So building fossil fuel plants is not always the best answer. Actually, there are other ways to make electricity without burning fossil fuels. People have been using the power of wind for centuries. Wind power won't solve all our energy problems, but it can help meet some of the demands in certain places. Since the late 1800s, scientists have been working to turn the sun's energy into electricity by using solar cells (太阳能电池). The problem is, solar cells are very expensive. Another way to make electricity is to use nuclear energy. It has been used for more than 50 years. Today about 10 percent of all the electricity used in the U. S. A. comes from this source. Although nuclear power doesn't pollute the air as the burning of fossil fuels does, there is a major drawback . The waste products from nuclear power plants are dangerous and must be stored in safe places. Many people are concerned about the safety of nuclear power. The best title for this passage may be ______.