What is the term for the gases that form the Earth's atmosphere?

The term that refers to the gases surrounding the Earth is "atmosphere." The atmosphere is a critical part of the planet's environmental system, consisting mainly of nitrogen and oxygen, along with traces of other gases such as carbon dioxide, argon, and water vapor. It plays a vital role in supporting life, regulating temperature, and protecting the Earth from harmful solar radiation.

Other options provided do not define the gases in the Earth's atmosphere. The hydrosphere relates to all of Earth's water bodies, including oceans, rivers, and lakes. The lithosphere pertains to the solid outer section of the Earth, including the crust and upper mantle. The stratosphere is a specific layer within the atmosphere located above the troposphere, primarily known for containing the ozone layer. Thus, atmosphere is the most appropriate term to describe the overall gaseous envelope that surrounds our planet.