The quality of a greenhouse gas you're describing sounds like it refers to a gas that absorbs and re-emits infrared radiation, which is characteristic of greenhouse gases in general. However, the point regarding being "composed of single items not molecules produced only by human activity" is a bit confusing.
If you are looking for a specific greenhouse gas that fits certain characteristics, one example might be carbon dioxide (CO2), which is produced by human activities, such as burning fossil fuels and deforestation. It is a molecule (not a single item), composed of one carbon atom and two oxygen atoms, and is known for its ability to absorb infrared radiation, contributing to the greenhouse effect.
Just to clarify:
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Absorbs and repels infrared radiation: Greenhouse gases, including CO2, methane (CH4), and nitrous oxide (N2O), contribute to the greenhouse effect by trapping heat in the atmosphere.
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Produced by human activity: Many greenhouse gases are significantly emitted due to human activities (e.g., industrial processes, agriculture, waste management).
If you meant something different—or if there’s a specific aspect of greenhouse gases you’re inquiring about—please clarify!