Final answer:
2)Carbon dioxide (CO₂) is the gas primarily responsible for the greenhouse effect and has become much more concentrated in the atmosphere due to human activities such as the burning of fossil fuels and deforestation.
Step-by-step explanation:
The gas primarily responsible for the greenhouse effect is carbon dioxide (CO₂). Water vapor accounts for about 80 percent of the natural greenhouse effect, with carbon dioxide, methane, and a few other minor gases contributing to the remainder.
However, among the gases emitted through human activities, carbon dioxide is the most significant. It is naturally present in the atmosphere as part of the Earth's carbon cycle.
But human activities such as the burning of fossil fuels and large-scale deforestation have greatly increased its concentration since the Industrial Revolution, thus enhancing the greenhouse effect and contributing to recent global climate change.
In addition to carbon dioxide, other greenhouse gases like methane (CH₄), nitrous oxide, and synthetic gases such as hydrofluorocarbons (HFCs) are also contributing to the enhanced greenhouse effect.
These gases trap heat in the atmosphere, preventing it from escaping into space, which leads to a warming effect similar to the function of glass panels in a greenhouse.