More than 100 years ago, Earth's atmosphere contained about 280 parts per million (ppm) of carbon dioxide. It is predicted that by the year 2050, the level of carbon dioxide in the atmosphere could reach 700 ppm, greatly increasing Earth's temperature. It has been suggested that growing more green plants
would help to slow this increase. The best explanation for why increased numbers of plants would help is that plants
serve as food for herbivores
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serve as a nonrenewable energy resource
remove carbon dioxide from the atmosphere during respiration
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remove carbon dioxide from the atmosphere during photosynthesis