A、They pollute the atmospheric environment. B、They produce dangerous gases. C、They stop the sun’s heat reaching the earth. D、The

The earth is getting warmer. People burn coal, oil and gas and this produces carbon dioxide, methane and nitrous oxide. These gases, called "greenhouse oxide", stop the heat of the sun from leaving the earth’s upper atmosphere and this makes the earth warmer, a process called "global warming".
    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. The scientists were shocked by what they found. They say that during the next 50 years about 25% of land animals and plants will become extinct. More than 1 million plant and animal species will become extinct by 2050.
    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 very long distances to get cooler, so they are in greater danger of extinction.
    Global warming is getting worse. Many countries, particularly the USA and the European countries, are continuing to produce greenhouse gases. We will not know the true results of this for 25 years but if people continue to burn oil, coal and gas at the same rate as today, about 30% of all life forms will become extinct by 2050.