1     (construct) from the 5th century BC, the Grand Canal was a means of communication for the Empire for the first time in the Sui Dynasty.

Before foundation of Sui Dynasty, China had     2     (continuous) evacuated several canals,     3     had been suspended due to natural environment. Some needed to be repaired but were still navigable, but were too separated from each other to form large-scale water transport nationwide.

The establishment of Sui Dynasty     4     (declare) the end of long-lasting split situation. In 605 AD, Emperor Yang Guang, the     5     (two) emperor of Sui Dynasty, ordered excavation of the Grand Canal to meet the political,     6     (economy) and military needs of unified nation.

The Grand Canal reached a new peak in the Yuan Dynasty (13th century), providing a unified inland navigation network consisting     7     more than 2,000 km of artificial waterways, linking five of the most important river basins in China,     8     (include) the Yellow River and the Yangtze.

As     9     major means of internal communication today, it has played an important role in ensuring the prosperity and     10     (stable) of China over the ages.

Placed among the busy streets of Washington, D. C. is a large public garden that many Americans have never heard of. The U. S. National Arboretum (植物园) includes     1     collection of flowering plants called azaleas, a field of native plants named ferns, and flowering trees in the dogwood tree area. The garden     2     (establish) by Congress in 1927. It plays a leading part in researching and developing plants like trees, shrubs, flowers, and grasses.

Government scientists are in charge of the 180-hectare area. Their main goal is     3    (strengthen) the U. S. economy by making sure an important kind of agriculture,     4     (call) the nursery industry, continues to perform well. The most recent numbers from the U. S. Department of Agriculture (USDA) show that the ornamental and landscape plant industry creates billions of founds in sales each year.

The arboretum is home to one of the     5     (large) collections of preserved seeds in the world. The National Arboretum Herbarium (植物标本)     6     (house) around 700,000 ex-ample seeds. They include seeds from plants that the USDA considers as     7    (economical) important. Scientists collect many genetically different seeds within a kind of plant from both native and non-native plants. The reason     8     collecting that data is that scientists protect plants from harmful situations like climate change, changed environments, or other new and possible risks.

While the scientists do their work, the public     9     (explore) plants is free to visit the arboretum. Though many people may not know it, the arboretum has had a hand in developing a number of plants     10     are part of American landscaping.

3 . The country’s first national park, Yellowstone, is renaming one of its largest mountains to honor indigenous people after research revealed the man it had been named after helped lead a massacre (屠杀) against local tribes. As part of the park’s 150th anniversary, officials announced the 10,551-foot high peak formerly called Mount Doane is now First Peoples Mountain.

“It is a victory, yes. Is history being rewritten and retold truthfully? I hope so,” William Snell, executive director of the Rocky Mountain Tribal Leaders Council, told NPR. His group helped advise federal officials on the name change. In an email, Snell said the change to First Peoples Mountain couldn't have come at a better time as Yellowstone officials prepare for the park’s anniversary in August.

The peak—along a range on the eastern side of Yellowstone Lake—had been named after Gustavus Doane, who helped lead the Washburn-Langford-Doane exploration in 1870 that eventually led to the park getting federal protection.

But recently, historians uncovered Doane’s role in an attack that left at least 173 Native Americans dead. Known as the Marias Massacre, Doane carried out the attack over the killing of a white fur trader. In writings, Doane cast a favorable light on the attack and even showed off about it for the rest of his life, the National Park Service said last week.

The renaming to First Peoples Mountain is part of a trend to better recognize the roles and contributions of Native Americans. It has also become a priority of the nation’s first indigenous cabinet secretary—the Interior Department’s Deb Haaland, who oversees the National Park Service—and Charles SamsⅢ, the first Native American to serve as that agency’s director.

Across the American West, many iconic representative mountains and other environmental places were named after early white settlers, mostly men and some with terrible pasts.

In Yellowstone, park officials say they may consider further changes to derogatory (贬损的) or inappropriate geographical names in the months ahead.

4 . Balmoral Castle

Balmoral Castle, which started in the late 1300s. is the private residence of the Queen. It has remained a favourite residence for the Queen and her family during August and September.

Some 85,000 people visit Balmoral each year, and the estate maintains and restores footpaths throughout the property for visiting hikers.

Windsor Castle

Windsor Castle is an official residence of The Queen and the largest occupied castle in the world. The castle was the inspiration for the Royal family’s surname.

William the Conqueror built the castle in 1080 and it has remained a royal palace for over 900 years. Windsor is the oldest royal home in Britain and, covering 13 acres, it’s the largest castle in the world that is still lived in.

Each year, the Order of the Garter ceremony is held at Windsor Castle, and the Queen occasionally hosts a “dine and sleeps”, for politicians and public figures.

The Palace of Holyroodhouse

Founded as a monastery (修道院）in 1128, the Palace of Holyroodhouse in Edinburgh is The Queen’s official residence in Scotland. It was also the home of many Scottish royals.

The Queen holds receptions, state functions, and investitures(授职仪式）within its walls, and each year during Holyrood Week Queen Elizabeth and Prince Philip invite 8» 000 Scottish guests to the Garden Party.

St. James Palace

St. James’s Palace was built between 1531 and 1536 and was home of kings and queens of England for over 300 years. The palace was built by Henry VU on the site of the Hospital of St. James, Westminster. After the destruction by fire of the Palace of Whitehall in 1698, all monarchs until William W lived at St. James's for part of the time.

The Xi’an City Wall is the most complete city wall that has survived China’s long history. It     1     (build) originally to protect the city     2     the Tang dynasty and has now been completely restored (修复). It is possible       3     (walk) or bike the entire 14 kilometers.

We accessed the wall through the South Gate. The wall is 12 meters high and from here you can see streams of people moving inside and outside the City Wall.

After     4     (spend) some time looking at all the defensive equipment at the wall, we decided it was time for some action and what     5     (good) than to ride on a piece of history!

We     6     (hire) our bikes from the rental place at the South Gate. My bike was old and shaky     7     did the job. It took us about 3 hours to go all     8     way around the Xi’an City Wall. Supposedly you can do it in two hours, but we stopped at the different gates and     9     (watchtower) to take pictures or just to watch the local people going about their     10     (day) routines.

6 . Stephen Warren, study leader at the University of Washington, has been on the case of the green icebergs for more than 30 years. He first took samples from one of these green hunks of ice in 1988, near the Amery Ice Shelf, East Antarctic. Most glacial ice occurs in shades of white to brilliant blue. The bluer the ice, the older it is. Typically, compression (压缩)from accumulating layers of snow pushes air bubbles out of the ice, reducing the scattering of white light. The compressed ice absorbs most of the light except for blue, creating the blue color seen in the hearts of icebergs and glaciers.

The green ice was similarly bubble-free, and yet it looked green instead of blue. Warren and his team soon found that the green ice came not from glaciers, but from marine ice. That's the ice from the undersides of floating ice shelves.

At first, the team thought that organic material in the marine ice was causing the green color. But further research showed that the green marine ice didn't have a higher — than — usual amount of organic impurities. Now, a new study finds that a different sort of impurity may be the root cause of the green ice. Warren and his colleagues report that the marine ice at the bottom of the Amery Ice Shelf has 500 times more iron than the glacial ice above.

This iron comes from the rocks under the Antarctic Ice Sheet, which are turned into fine powder as glaciers move over them. The icebound iron oxidizes (氧化)as it contacts seawater. The resulting iron oxide particles take on a green color when light scatters through them. When icebergs break off the larger ice shelf, they carry this iron-rich ice with them. It's like taking a package to the post office. The iceberg can deliver this iron into the ocean far away, and then melt and deliver it to other living things that can use it as a nutrient.