The correct answers are C. methane and D. fluorinated, representing two recognized categories of greenhouse gases included in international emissions reporting frameworks.
According to the United States Environmental Protection Agency (EPA), the principal anthropogenic greenhouse gases include carbon dioxide, methane, nitrous oxide, and fluorinated gases.
US EPA
Methane (CH₄) is produced through natural and human activities, including fossil fuel extraction, livestock farming, landfills, agricultural processes, and organic matter decomposition.
Methane absorbs infrared radiation and contributes significantly to atmospheric warming. Its global warming potential is substantially greater than carbon dioxide over a 100-year assessment period.
Fluorinated gases, commonly called F-gases, comprise several industrially produced substances, including hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride.
These gases are used or generated in refrigeration, semiconductor manufacturing, industrial processing, and electrical equipment.
Many fluorinated gases have extremely high global warming potentials and long atmospheric lifetimes.
US EPA
Carbon monoxide is generally classified as an indirect greenhouse gas because it influences atmospheric chemistry.
Butane can absorb infrared radiation but is not one of the principal greenhouse gases separately reported under standard corporate GHG inventories.
Poly dioxide is not a recognized greenhouse gas classification.
Therefore, methane and fluorinated gases are the two intended answers.
[Reference: Cisco Environmental Sustainability Course Guide, Defining Sustainability — Greenhouse Gas Emissions. US EPA, Overview of Greenhouse Gases; Fluorinated Gas Emissions.]
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