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[单项选择] Carbon dioxide makes up less than one percent of the Earth’s atmosphere. But the gas is very important to life on Earth. Scientists are finding that processes involving carbon dioxide affect our climate in ways that are difficult to understand.
Last month, a committee of the National Academy of Sciences in Washington released a report. It confirmed that world temperatures increased about six-tenths of a degree Celsius in the last one hundred years. The report also confirmed evidence that the level of carbon dioxide is increasing.
The best information about climate in the past comes from tests of ice many kilometers deep in Antarctica and Greenland. The tests show changes in temperature during the past four-hundred-thousand years. These tests show that levels of carbon dioxide today are the highest ever measured. These findings have led scientists to believe that carbon dioxide is a major cause of climate warming.
Carbon dioxide is released into the atmosphere when fuel i
A. they think that carbon is beneficial for plant growth
B. they want to use more fuels that can emit carbon dioxide
C. they think carbon dioxide is not the main reason for global warming
D. they think it will destroy the natural balance of gases in the world