Final answer:
Chlorofluorocarbons (CFCs) are the only greenhouse gas entirely produced by human activities. Other gases such as Methane, Carbon dioxide, and Nitrous oxide have both natural and human-made sources.
Step-by-step explanation:
The only greenhouse gas among the options listed that is entirely produced by human activities is Chlorofluorocarbons (CFCs). CFCs are not naturally occurring and were first created in the early 20th century for use in air conditioning, refrigeration, blowing agents for foams, insulation, and aerosol propellants. Other gases such as Methane, Carbon dioxide, and Nitrous oxide have both natural and human-made sources. For example, Methane is produced naturally in wetlands and tundra, and it's also released through human activities like fossil fuel extraction and livestock farming. Carbon dioxide is produced naturally through respiration and volcanic eruptions, beside human activities like burning of fossil fuels and deforestation. Nitrous oxide is produced naturally from a wide variety of biological sources in soil and water, particularly microbial action in wet tropical forests, beside human-induced sources like agricultural activities and burning fossil fuels.
Learn more about Greenhouse gases