In ancient times, all roads     1     (lead) from the outside to Sichuan were referred to as the Shu Path, including those from Shaanxi and Gansu.

Surrounded by mountains, Sichuan, called Shu in ancient times, was known for its inaccessibility. That became widely known partly due to a line from Chinese poet Li Bai,     2     reads “Traveling on the Shu Path is as difficult as climbing to heaven”. The most famous section of the Shu Path is about 600 kilometers long. It starts at Chengdu, and then passes Deyang and Guangyuan in Sichuan before ending in Hanzhong in Shaanxi. The     3     (construct) of the section started around 316 BC. It was on such     4     (danger) mountains that Li Bai was inspired     5     (mention) it.

When builders approached the Mingyue Gorge in Guangyuan, they found     6     impossible to continue because of high cliffs (悬崖). So they dug three levels of holes in the rock, and put in wooden beams. The upper beams were     7     (complete) covered by planks (木板) to form a road for people to walk on. The plank road     8     (rebuild) many times during wars. Now part of it has been restored to allow visitors to admire the man-made wonder.

The Sword Gate Pass, a towering V-shaped mountain pass—the one that gave rise     9     a household idiom, “One man at the pass keeps 10,000 men at bay”—witnessed countless battles during the Three Kingdoms and     10     (be) a tourist attraction now in the Guangyuan section of the Shu Path.

The Potala Palace (布达拉宫) features a wall painting     1     illustrates a historic marriage between members of the Han and Tibetan ethnic groups. Like the wall painting, many other relics in Tibet have also helped     2    (far) uncover cultural communication between Tibet and the rest of China.

    3    (original) built in the eighth century, the Samye Monastery is listed as an example of a combination of cultural heritage and architectural styles, while the Shalu Monastery, set up in 1087, is another example of a mix of architectural styles.

The earliest archaeological site     4    (identify) at the heart of the Qinghai-Tibet Plateau (高原) so far is the Nwya Devu site. More than 4,000 stone artifacts (石器)     5    (find) at the Paleolithic site since 2016. Scientific analysis shows that the site     6    (date) back to some 40,000 years ago.

Archaeological     7    (discovery) have also provided abundant evidence of cultural integration. For example, the wooden carving unearthed from Tibet’s Ngari and those from Xinjiang are similar     8     shape.

The cultural     9    (connect) between Tibet and the Yellow River basin was proved at the Karub ruins with the finding of a crop planted in northern China. The finding proved     10     communication between the plateau and northern China some 5,000 years ago.

5 . When it comes to planning a student trip, there are few better choices than our nation’s capital. There are many places of interest in Washington, DC, with sites that will attract students who are interested in everything from history, art, to STEM. Don’t miss these must-see sites on your trip to Washington, DC.

Managed by the Smithsonian Institution, admission (入场券) is free, and all locations are open every day except December 25. Students will love the exhibitions of the National Air and Space Museum, and everyone can enjoy the National Zoo, which is home to giant pandas, Sumatran tigers, and much more.

This is an amazing place for students interested in art. It includes the East Building and the West Building and houses the gallery’s more modern works and a collection of older works. The museum welcomes visitors from 10 am to 5 pm from Monday to Saturday and 11 am to 6 pm on Sundays. There is a variety of free self-guided and audio (音频) tours available.

The Newseum aims to increase public awareness of the importance of a free press. Visitors can experience the story of news, the role of a free press in major events in history and how freedom of speech is applied to their lives.

Only 16 miles south of Washington, DC lies Mount Vernon, George Washington’s home. This historic place features beautiful gardens and wonderfully kept grounds. The outbuildings surrounding the main house still run today. Visitors can tour these structures in addition to the inside of the main house and go there by subway.

The Jiaohe Ancient City Ruins,     1     (locate)10 kilometers west of Turpan, Xinjiang Uygur autonomous region is the largest, oldest and best-preserved earthen architectural site in the world,     2     holds great political, cultural, historical and artistic value.

Guri Bakri, a 39-year-old conservator of the Jiaohe Ruins, starts her daily inspection at the site as usual, ensuring the safety of tourists and     3     (make) photographic records along the way. She is the third generation of Guri’s family who have been working as local cultural conservators,     4     (constant) guarding this historic site since her grandfather     5     (become) the only conservator in Jiaohe in 1961.

After graduating in 2013, Guri returned to her hometown and became one of her father’s     6     (colleague). Talking about Jiaohe, Guri said that she would always remember June 22, 2014, when the Jiaohe Ancient City Ruins     7     (name) the World Heritage Site. She was proud of her participation in the application     8     the title.

In recent years, the state cultural protection department has invested more than 100 million yuan ($ 14.8m) in the     9     (protect) of Jiaohe Ancient City Ruins. This year, Jiaohe Ancient City Ruins will take the fifth round of structural reinforcement (加固).     10     team of conservators has also expanded to 12. This old city of more than 2,000 years is gaining new energy.

8 . In April 2018, a group of Canadian scientists flying in a helicopter (直升飞机) discovered something they didn't expect to see — a huge, unknown cave with an opening the size of a football field.

The cave was discovered in the northern part of Wells Gray Provincial Park, in a wild, faraway area of Canada's Cariboo Mountains. The area is hard to get to and even harder to travel through. It is covered with snow for much of the year.   

The group told Catherine Hickson, a scientist who studies rocks, about the cave. Dr. Hickson got a team of researchers together to study it. In September, they went for a closer look after most of the snow melted (融化). The cave is one of the largest in Canada. Not only is the opening to the cave larger than a football field, the cave is also deep. The team couldn't measure (测量) all the way to the bottom, but they think it may be more than 180 meters deep. The cave is tens of thousands of years old. But the rock in the cave is made of used to be at the bottom of an ocean (海洋). It is hundreds of millions of years old.

A small, but fast river of melting snow leads into the cave on one side, creating a waterfall near the top and a river at the bottom. The water comes out again a long way away. The exit (出口) is about 2.1 kilometers away and about l/2 kilometer lower down.

The cave will have to wait to get an official name. For now, the cave is being called "Sarlacc's Pit "because it looks similar to the home of the Sarlacc, a person in the Star Wars movie Return of the Jedi.

For Dr. Hickson, there's a lesson to be learned from the cave. "It shows you that you don't know everything, "she says." There are things yet to be discovered."

9 . When you think of the icy Arctic Ocean, do you picture cold blue waters, on which float (漂浮) icebergs home to animals and fish not seen elsewhere on the planet? Think again, or rather add 300 billion pieces of plastic (塑料) to your picture. That's the amount of plastic that scientists believe is floating around the Arctic Ocean. Most of the plastic is in the area to the east of Greenland and north of Scandinavia.

Where did it come from? After all, the lands near the Arctic are not really full of people. It turns out that ocean currents are carrying plastic thrown into the ocean all the way to the Arctic. An ocean current is an unending movement of sea water from one point to another. It is caused by several things including heat from the Sun, wind and movement of the Earth.

Many of these plastic pieces seem to have travelled for years before reaching the Arctic. This was worked out by scientists studying the plastic problem after they observed the condition of the pieces. While much plastic floats on top of the water, a lot also may be on the sea floor.

Plastic has been widely used for 60 years on Earth and our careless throwing of plastic things is slowly turning the once perfectly clean Arctic into a dangerous place. Unlike food waste and plant waste, plastic doesn't break down so easily. In fact the United States Environment Protection Organization reports that “every bit of plastic ever made still exists”.

What's the effect? Seabirds, sea turtles and other ocean creatures could get hurt and die when they accidentally swallow plastic. Plastic waste affects fishing, affecting people who earn money through fishing. Plastics can let out dangerous poisons (毒物) into the water. These may be swallowed by fish, and when these fish are caught and eaten by people or bigger animals, they could get poisoned too!