Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.

The tourist industry is considered 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 ___(14)___ worldwide reached 1.04 billion in 2012.

Such large members of tourists, ___(15)___, are beginning to cause problems. For example, in the Alps the many thousands of skiers are destroying the mountains they came to enjoy. Even parts of Mount Everest in the Himalayas are reported to be covered ___(16)___ old food tins, tents, and pieces of equipment that have been thrown away. At a time when we have greater freedom to travel ___(17)___ ever before, more and more people are asking how they can enjoy their holidays without causing damage to their destinations.

Now there is a new holiday guide called "Holidays That Don't Cost The Earth". It tells you how you can be a responsible tourist by asking your travel agent or your tour ___(18)___ the right questions before you book a holiday.