What is a characteristic of a greenhouse gas?

A characteristic of a greenhouse gas is that it contributes to the greenhouse effect. Greenhouse gases, such as carbon dioxide, methane, and nitrous oxide, are capable of trapping heat in the Earth's atmosphere. When sunlight reaches the Earth's surface, it is absorbed and then re-radiated as infrared radiation. Greenhouse gases absorb and emit this radiation, preventing heat from escaping into space and thus warming the planet. This process is essential for maintaining the Earth's temperature and supporting life, but an excess of greenhouse gases due to human activities can lead to climate change and global warming.

The other options, while they may describe certain gases, do not capture the defining feature of greenhouse gases in relation to climate dynamics.