What gases are predominantly found in the troposphere?

The troposphere is the lowest layer of Earth's atmosphere, where we live and where most weather phenomena occur. It extends from the Earth's surface up to about 8 to 15 kilometers (5 to 9 miles) in altitude, depending on geographic location and weather conditions. The main gases present in the troposphere are nitrogen and oxygen, which together make up about 99% of the atmosphere by volume.

Nitrogen is the most abundant gas, constituting about 78% of the atmosphere, and oxygen follows with around 21%. These gases are essential for life on Earth; oxygen is crucial for respiration in animals and many forms of plant life, while nitrogen plays a critical role in the biological processes of organisms, including the formation of amino acids and nucleic acids.

The other gases listed in the other choices, while they exist in the troposphere, are present in much smaller concentrations. Carbon dioxide and ozone are important trace gases but do not make up the primary composition of the atmosphere. Helium and argon are noble gases and are found in very small amounts, and hydrogen, while present in trace amounts, is not a significant component of the tropospheric gas mixture. Thus, the predominant gases in the troposphere are