The people who built Stonehenge in southern England thousands of years ago had wild parties, eating barbecued pigs and breaking pottery. This is according to recent work by archaeologists — history experts who investigate (调查) how human beings lived in the past.

    Archaeologists digging near Stonehenge last year discovered the remains of a large prehistoric village where they think the builders of the mysterious stone circle used to live.

    The village is about 4,600 years old, the same age as Stonehenge and as old as the pyramids in Egypt. It is less than two miles from the famous ancient landmark and lies inside a massive man­made circular dirt wall, or "henge", known as the Durrington Walls.

    Remains found at the site included jewellery, stone arrowheads, tools made of deer antlers, wooden spears and huge amounts of animal bones and broken pottery. "These finds suggest Stone Age people went to the village at special times of the year to feast and party", says Mike Parker Pearson from Sheffield University in England.

    He said many of the pig bones they found had been thrown away half-­eaten. He also said the partygoers appeared to have shot some of the farm pigs with arrows, possibly as a kind of sport before barbecuing them.

    An ancient road which led from the village to the River Avon was also found. Here, the experts think, people came after their parties to throw dead relatives in the water so the bodies would be washed downstream to Stonehenge.

    Parker Pearson believes Stonehenge was like a cemetery where ancient Britons buried the dead and remembered their ancestors. "The theory is that Stonehenge is a kind of spirit home to the ancestors."

    The recent discovery of the village within the Durrington Walls shows that Stonehenge didn't stand alone but was part of a much bigger religious site, according to Parker Pearson.

    People still come to worship and celebrate at Stonehenge today. They meet there when the sun sets on the shortest day of winter and when it rises on the longest day of summer. But the days of barbecuing whole pigs there and throwing family members into the river are a thing of the past.

    Street art is a very popular form of art that is spreading quickly all over the world. You can find it on building, sidewalks, street sings and trash cans from Tokyo to Paris, and from Moscow to Cape Town. Street art has become a global culture and even art museums and galleries are collecting the works of street artists. Even advertising companies also use street art in their ads due to its popularity.

    Street art started out very secretly because it's illegal to paint on public and private property without permission. People often have different opinions about street art. Some people think it is a crime with others think it's a new form of culture.

    Art experts claim that the movement began in New York in the 1960s. Young adults sprayed words and images on walls and trains. This colorful and energetic style of writing became known as graffiti(涂鸦). Graffiti art showed that young people wanted to rebel against society. They didn't want to accept rules, and they travelled around cities to create paintings that everyone could see. In many cases, they had trouble with the police and the local government.

    Many street corners in Paris show the works of Space Invader. A French artist uses small pieces of glass to make images of space creatures. He has been doing this for some years and the police have arrested him a few times. On his website, you can see many other places where he has created this form of art.

    Street artists do their work for some reasons. Some of them do not like the artists who make so much money in galleries and museums. They choose street art because it is closer to common people. Some artists try to express their political opinion in their works. They often want to protest against big firms and corporations. Others like to do things that are forbidden and hope they don't get caught.

    In today's world, the Internet has a big influence on street art. Artists can show their pictures to people all over the world. Many city residents, however, say that seeing a picture on the Internet is never as good as seeing it alive. The street art movement lives with the energy and life of a big city. There it will continue to change and grow.

下图中阴影表示非洲北部萨赫勒地区（撒哈拉沙漠南部向热带草原过渡的干旱、半干旱地带），当地牧民每年赶着大量牲畜于11月南迁，6月北移，近年来该地区植被退化严重。据此回答：

能够实时反映这种植被破坏状况的技术手段是（   ）