The tourist industry (25) to be the world's largest industry. The direct economic impact of the industry, including accommodation, transportation, entertainment, and attractions, is worth trillions of dollars every year. The statistics show that the number of international tourist arrivals worldwide reached 1.04 billion (26) 2012.
Such large numbers of tourists, however, are beginning to cause problems. For example, in the Alps, thousands of skiers (27) the mountains they come to enjoy. Even parts of Mount Everest in the Himalayas are reported to be covered with old food tins, tents, and pieces of equipment that have been throw n away.
Now there is a new holiday guide which is called Holidays That Don’t Cost the Earth. It tells you how you can be a responsible tourist by (28) your travel agent or your tour operator the right questions before you (29) a holiday.

Many people still believe that natural resources will never be used up. Actually, the world’s energy resources are limited. Nobody knows exactly how much fuel is left. However, we also should use them economically and try to find 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.
However, many people do not approve of using nuclear power because it’s very dangerous. What would happen if there were 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 economically as possible.