Have you ever heard of Death Valley? It’s a national park lying in the east of California, the USA. The park isn’t scary as its name sounds. You can enjoy the desert sunshine there. At the same time, you can find there’s nothing out there but some special rocks called “sailing stones” . Some of the rocks in Death Valley weigh hundreds of pounds. And on the ground behind each rock is a mysterious trail(痕迹). It seems that the rock has been pushed along in the sand.

It was nearly 100 years ago that the “sailing stones” were reported for the first time. People have been trying to find out the stones’ secret ever since. Until the 1990s, one widely accepted opinion was that the rocks were stuck in sheets(片) of ice that were being blown across the desert. However, research later showed that to move such large ice sheets, the wind would have to blow at hundreds of miles per hour. There are strong winds in Death Valley, but not that strong.

Then in 2006, a scientist named Ralph Lorenz expressed his opinion. He suggested that in winter, thick ice forms(形成) around the rocks. When the ground begins to thaw(解冻), the rocks, wearing ice, sail along and leave trails behind them. Lorenz even did a test in his own kitchen for the purpose of showing his opinion was correct.

Has Lorenz succeeded in solving the mystery of the sailing stones? Perhaps. On the other hand, neither Lorenz nor anybody else has ever actually seen the stones move. Maybe it was aliens who moved the stones.

Rainforests are very large, they can be found close to the equator（赤道）, in South East Asia, West Africa and Central and South America. They have very high temperatures and it rains all year round. In a year it can rain as much as 260 cm!

The rainforest is divided into three layers（层）. The canopy（树冠）is the top layer of the trees where most of the animals live. These trees can be more than 30 meters high and it is the noisiest layer of the rainforest. The middle layer is under the canopy and has some shorter trees. The third layer is the forest floor. It has very little sunlight and is the quietest layer of the rainforest. It can take ten minutes for a falling raindrop to travel from a rainforest’s thick canopy to the floor.

Rainforests help to protect the Earth’s climate（气候）because they take in CO₂, a greenhouse gas from the air, and give out O₂. Many things we need such as medicines and food come from the rainforests, too.

Unluckily, these rainforests are disappearing. Every second an area the size of a football field is either cut down for wood, to make furniture（家具）, to build houses or to be cleared for farming animals. Action needs to be taken to protect the rainforests now!

South Australia is a great place to visit. There are a lot of animals, beautiful flowers and interesting places. Do you want to play with koalas? You can do many things you want to do.

It's a good place for children. There are many things for children to do. They can have a lot of fun. They can run around with the animals. They can swim with sea lions and dolphins. They can even pet (抚摸) the koalas on the head in wildlife parks because they are very friendly.

Children can relax on the long beaches. They can go swimming there. They can visit the national parks, too.

Go there and enjoy yourself! You will enjoy it.