Read the following passage and choose the item (a, b, c, or d) that of the questions about it. Although they are safe to use in the short term, coal, gas and oil present a long-term threat to the environment. All three types of fossil fuels produce carbon dioxide in far greater quantities than plants can use. The carbon dioxide then accumulates in the atmosphere and may even increase the earth’s ‘heat load’ and lead to global rises in temperature. Thus, contrary to popular belief. the use of coal, gas and oil is not as safe as was originally thought. Furthermore, all three fossil fuels are non-renewable forms of energy. Hydro-power (in the form of waterfalls and dams) offers a much more useful source of energy. It is also renewable but its availability is limited. Dams cannot be built in certain areas. In addition, dams may have a damaging effect on a locality, resulting in the loss of farming land and the silting up of rivers. Large dams are also capable of causing changes in the world’s climate. Solar power is renewable, it does not cause pollution and it does not add to the earth’s heat load. Unfortunately, solar power is not distributed equally, and in northern latitudes it is difficult to collect and store. Solar power also requires expensive equipment. Finally, nuclear power provides a very efficient and renewable power source. However, not only is there a great danger of leaks or accidents but there is also the problem of the disposal of radioactive waste. Question 46. Fossil fuels _____.
