根据短文内容，从下框A~F选项中选出能概括每段主题的最佳选项，并在答题卡上将该选项涂黑。选项中有一项为多余项。

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The earth is getting warmer. People burn coal, oil and gas and this produces carbon dioxide, methane (沼气) and nitrous oxide. These gases, called “greenhouse gases”, prevent the heat of the sun from leaving the earth’s upper atmosphere and this makes the earth warmer.
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A few weeks ago a group of scientists produced a report about global warming and the natural world. They wanted to find out if global warming was dangerous for plants and animals. According to what they found, the scientists say that during the next 50 years about 25% of land animals and plants will become extinct (灭绝). More than a million plant and animal species (物种) will be extinct by 2050.
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More than 10% of all plants and animals will become extinct. It is too late to save many plants and animals because of the greenhouse gases that are already in the atmosphere. But the scientists say if we control greenhouse gases now, we could save many more plants and animals from extinction.
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The scientists studied some regions of the world with a very rich biology. These regions were Europe, Australia, Central and South America, and South Africa. Their studies showed that species living in mountainous areas had a better chance of survival because they could move uphill to get cooler. In flat areas, such as deserts, plants and animals would have to move a very long distance to get cooler, so they are in greater danger of extinction.
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The scientists found that half of the 24 species of butterflies they studied in Australia would soon become extinct. 60% of the species in the Kruger National Park in South Africa would also die out, and more than 100% of the 300 South Africa plant species they studied would also become extinct. One of the plants in danger of extinction is the national flower of South Africa, the King Protea. They studied 163 tree species in the Cerrado region of Brazil and found that 70 would become extinct. Many of the plants and trees that live in this region live nowhere else in the world. In Mexico, they studied 1,870 species and found that more than 30% of these were in danger of extinction.