GRE Reading Comprehension

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Source: XDF

The molecules of carbon dioxide in the Earth's atmosphere affect the heat balance of the Earth by acting as a one-way screen. Although these molecules allow radiation at visible wavelengths, where most of the energy of sunlight is concentrated, to pass through, they absorb some of the longer-wavelength, infrared emissions radiated from the Earth's surface, radiation that would otherwise be transmitted back into space. For the Earth to maintain a constant aver age temperature, such emissions from the planet must balance incoming solar radiation. If there were no car-bon dioxide in the atmosphere, heat would escape from the Earth much more easily. The surface temperature would be so much lower that the oceans might be a solid mass of ice.

Question List: 1 2

According to the passage, the greatest part of the solar energy that reaches the Earth is

  • A concentrated in the infrared spectrum
  • B concentrated at visible wavelengths
  • C absorbed by carbon dioxide molecules
  • D absorbed by atmospheric water vapor
  • E reflected back to space by snow and ice

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