Which of the following is true regarding greenhouse gases?

Greenhouse gases are primarily characterized by their molecular structure, which typically includes three or more atoms. This is significant because molecules with three or more atoms are capable of absorbing and re-emitting infrared radiation, which is a key mechanism by which they trap heat in the Earth's atmosphere. This heat retention is essential for maintaining the planet's temperature and sustaining life.

In contrast, gases with only one or two atoms, such as nitrogen (N2) and oxygen (O2), do not contribute to the greenhouse effect because they lack the necessary vibrational modes to absorb infrared radiation. Additionally, while many greenhouse gases are indeed produced by human activities, some, like water vapor and carbon dioxide, occur naturally and are part of the Earth's natural processes. Lastly, stating that greenhouse gases do not trap heat is fundamentally incorrect, as their primary function in the atmosphere is to retain warmth, contributing to what is known as the greenhouse effect.