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What does the last sentence of the passage most probably mean？
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According to paragraph 4, what were the subjects required to do during the experiment？
How did the museum collect the data in the Central African Republic？
Urban Rainforest
On the west side of the island of Manhattan in New York City, tree by tree, leaf by leaf, a 2,500 square foot sector of the Central African Republic's Dzanga Ndoki Rainforest has been transported to, or recreated at, the American Museum of Natural History's new hall of biodiversity. When the hall opens this May, visitors will visit one of the world's biggest and most accurate reproduction of one of nature's most threatened creations.
To bring the rainforest to New York, a team of nearly two dozen scientists — the largest collecting expedition the museum has ever organized for an exhibit — spent five weeks in the African rainforest collecting soil, plants, and leaves: recording and documenting species; studying trees; shooting videotape and still photos: and interviewing local people. "This area has been explored very little," says Hoel Cracraft who estimates that the museum will eventually collect 150 to 180 mammals, more than 300 species of birds, hundreds of butterflies, and hundreds of thousands, if not millions, of organisms. The exhibition may even have produced a special prize — scientists suspect they have uncovered several new species.
To give the forest a sense of realness, the back wall of the exhibit is an enormous ,video screen, sounds will come out from hidden speakers, and plans even call for forest smells. Computer controls will vary the effects so that no two walkthroughs will ever be exactly the same.
After the team returned to New York, the forest was reproduced with the help of the computer. Computer Modelling programmes plotted distances and special relationships. Artists studied photos and brought what they saw to life. Plaster trees were made. Recreated animals began to stand in the rainforest of the hall. Flying creatures will hang from the ceiling. The light in the forest — one of the exhibit's cleverest re-creations — will seem real. Long tube lights will have the correct colour and temperature to produce a natural effect. The plants and animals exhibited throughout the hall exist naturally in a perfect balance — remove one, and the whole is imperfect if not endangered. The exhibit is proof to the hope that the world's rainforests will never exist solely as a carefully preserved artifact.
What is this passage mainly about？
Monarch without a Kingdom
This November, a hundred million butterflies will drop from the sky over Mexico, like autumn leaves. But for how long？ Genetically modified maize (玉米) could mean extinction for this beautiful butterfly, Rafael Ruiz reports.
Although its body is about 3 cm long and it only weighs 1 gm, the Monarch butterfly manages to travel 5,000 km each year. It seems to be so fragile, but its long journeys are proof of its amazing ability to survive. This autumn, the Monarch butterfly will once more set out on its journey from the US. It will keep going until it reaches Mexico. It travels these huge distances to escape the cold weather in the north.
In November, millions of Monarchs fall like bright, golden rain onto the forests in the mountains of central Mexico. In the silence of these mountains you can hear a strange flapping (拍动) of wings, as the Monarchs arrive at their destination. In the mountains, which reach a height of 3,000 metres, the butterflies are safe.
Before reaching their journey's end they have faced strong winds, rain. and snowstorms and they do not all manage to reach their destination. When the winters are really bad, perhaps 70 per cent of them will not survive. Their long journey to Mexico is thought to be one of the most amazing events in the whole of the American continent. When they get there they will stay until the beginning of April, when their internal calendar tells them that it is time to go back. The long journey, with all its dangers, begins again.
These delicate creatures now face danger of another kind - from scientific progress. In the US, millions of farms grow genetically modified maize which is pure poison for the butterfly. Laboratory experiments have shown that half of the butterflies which feed on the leaves of genetically modified maize die within 48 hours. Not all experts agree that this variety of maize is responsible for the threat to the Monarchs. In spite of these doubts, the European Union has refused to approve new crops of genetically modified maize until further investigations have been carried out.
Greenpeace is campaigning against genetically modified products (in Spain, there are already 20,000 hectares of modified maize). The environmental organization recently published a list of 100 species of butterfly in Europe alone which are threatened with extinction.
The Monarch butterfly travels 5,000 km each year.
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