短文还原：In Australia there is a famous island called Fraser Island. A great many visitors come here for holidays every year. Why? The reason is that it is special. (56)__________________. In fact, it is the largest sand island in the world. It’s about 200 kilometers long and 240 kilometers wide. Though the island is a popular place of interest, there is no airport on the island. The long beach along the east coast works as the airport. (57)______________. On the island there are sand hills without any plants, but there are forests with old trees, beautiful flowers and over a hundred lakes, too. (58)______________. Every year, visitors come to enjoy the island’s natural beauty. People like camping and hiking there. (59)______________. Animals were killed for food and this made them in danger of extinction (灭绝). They threw rubbish everywhere, and the lakes were seriously polluted. (60)______________. Rules have been set up. For example, visitors are not allowed to use motorboats (摩托艇) or go fishing in the lakes, and they mustn't leave any rubbish.