Without proper planning, tourism can cause problems. For example, too many tourists can crowd public places' that are also enjoyed by the inhabitants of a country. If tourists create too much traffic, the inhabitants become annoyed and unhappy. They begin to dislike tourists and to treat them impolitely. They forget how much tourism can help the country's economy. It is important to think about the people of a destination and how tourism affects them. Tourism should help a country to keep the customs and beauty that attract tourists. Tourism should also advance the well-being of local inhabitants. Too much tourism can be a problem. If tourism grows too quickly, people must leave other jobs to work in the tourism industry. This means that other parts of the country's economy can suffer. On the other hand, if there is not enough tourism, people can lose jobs. Businesses can also lose money. It costs a great deal of money to build large hotels, airports, air terminals, first-class roads, and other support facilities needed by tourist attractions. For example, a major international-class tourism hotel can cost as much as 50000 dollars per room to build. If this room is not used most of the time, the owners of the hotel lose money. Building a hotel is just a beginning. There must be many support facilities as well, including roads to get to the hotel, electricity, sewers to handle waste and water. All of these support facilities cost money. If they are not used because there are not enough tourists, jobs and money are lost. Which of the following has most probably been discussed in the para. that goes before the para. ? ______.