Many people still believe that natural resources will never be used up. Actually, the worlds energy resources are limited. Nobody knows exactly how much fuel is left. However, we also should use them economically and try to find out alternative sources of power. According to Professor Marvin Burnham of the New England Institute of Technology, we have to start conserving coal, oil and gas before it is too late; and nuclear power is the only alternative because it is very clean and unlimited. However, many people do not approve of using nuclear power because of its danger, especially when unexpected risks happen. What would happen if there was a serious nuclear accident? Radioactivity causes cancer and may badly affect the future generations. The most effective thing is that we should use natural resources as economical as possible. 36. Many people still believe that natural resources will never be ______. A. reduce B. risen C. run out D. raised 37. According to the writer, wed better use energy resources ______. A. economically B. regularly C. financially D. less 38. The word approve in the passage is closet in meaning to ______. A. disagree B. agree C. improve D. explain 39. ______ causes cancer and may badly affect the future generations. A. Coal B. Fuel C. Radioactivity D. Electricity 40. Which of the following is NOT true about nuclear power? A. clean B. safe C. risky D. dangerous