The Singing Sand Mountains are situated in Dunhuang in western China. As one of the coolest natural phenomena on     1     planet, the dunes sound as if they are singing to you as you slide down them.     2     (locate) between the tall dunes, there is a little miracle. This spring,     3     looks like a moon, has been there for thousands of years and has never dried up. The spring, even with the shifting sand,     4     (remain)blue year-round.

Climbing to the top of the dunes is hard work, but worth it. Rent a pair of bright-orange shoe protectors or just shake your     5     (shoe) out later as most people do. A wooden walkway is half buried in the sand so you can get a proper footing on the deep sand.

The dunes are a tourist     6     (attract), with dune cars, dune surfing, and helicopter flights. However,     7     (appreciate) the sandy scene in peace is not hard to hike away. The dunes look most attractive either in the morning     8     towards dusk.

The drive down the dunes is also     9     (surprise) as the large mountains of sand     10     (sudden) appear at the end of the road.

In the remote far north of Sweden in Sarek National Park, I wake up to the sound of the wind     1     (buffet) the cloth of my tent. Standing at     2     edge of the mountain, I see the Rapa River flow through the valley below.

Once     3     (cover) by vast sheets of ice, Sarek's mountains are home to the Sami,     4     are the native residents of the park. The Sami lived off reindeer, moved with them, and     5    (accompany) them for hundreds of years. Today, most Sami have left their ancient     6    (cottage) in the mountain valleys and live a modern life in villages near Sarek instead.

To keep its     7     (nature) state, apart from the Sami, no one is allowed     8     (live) in Sarek,     9     all new development is banned within the park boundaries.     10     is hoped that Sarek National Park will always remain as it is.

Rainbows are often seen     1     signs of hope. And we are likely to see more of them due to global warming, according to a new study in the journal Global Environmental Change.

The research team     2     (gather) 121, 558 rainbow pictures from the Internet taken between 2004 and 2019 and then used the photos to form a database which made it possible for the researchers     3     (learn) the patterns of how rainbows occur.

Rainbows, only appear with a     4     (suit) angled position of the sun, rainfall, and fewer clouds.

Due to the emission of greenhouse gases, there will be more rainfall and fewer clouds,     5     (lead) to more rainbows in the future.

The team also predicted that global rainbow     6     (occur) might increase by 4 to 5 percent by 2100. However, some places in the world may witness fewer rainbows. For example, the climate in tropical areas in Africa and South America may be     7     (dry) with less rainfall.

The researchers also called on more studies about     8     people’s lives can be affected apart from the changes we are already familiar with. “    9     (shift) in intangible (无形的) parts of our environment — such as sound and light — are part of these changes and deserve more attention from researchers, ”     10     lead author of the study Kimberly Carlson said to Science X Network.

September usually marks the start of a new season. In the UK, people will tell you it’s “autumn”. However, across the Atlantic people tend     1     (use) both “fall” and “autumn” when referring to this time of year. Why does it have to be so     2     (confuse)?

Before both words came into     3     (exist) in the vocabulary, the seasons separating the cold and warm months didn’t have common names. The main work people did during the pre-winter period was harvesting crops, so it     4     (call) “harvest” in Old English.

Then, in the 1600s, more people left the farmland and moved into cities.     5     farming, the term “harvest” became less useful to citizens. Some English speakers needed     6     different name for the season. They knew     7     (leaf) fell from trees during that season, so people called the season “the fall of the leaf”, or “fall” for short.

But by the end of the 1600s, autumn,     8     came from the French word “autompne”, had been introduced in England and overtook (超过) “fall” as the standard term for the harvesting season. At the same time, some British were making their first voyages to North America. They     9     (bring) “fall” and “autumn” with them. Today, using both words to describe the season is     10     (unique) American.