Define 'greenhouse gases'.

Greenhouse gases are specific gases in the Earth's atmosphere that have the capability to absorb and emit infrared radiation, which results in the trapping of heat. This process is critical for maintaining the Earth's temperature, as it allows the planet to retain some of the energy it receives from the sun, creating a suitable environment for life. Common greenhouse gases include carbon dioxide, methane, nitrous oxide, and water vapor. Their presence is vital for the natural greenhouse effect, which helps to sustain life by keeping the Earth warm enough to support ecosystems.

The other options do not accurately describe greenhouse gases. Some gases that may aid agricultural growth or be emitted during volcanic eruptions do not have the same role in trapping heat. Additionally, the notion of gases that cool the atmosphere does not apply to greenhouse gases, as their primary function is to warm the atmosphere through heat retention.