Which gases are considered the main components of the Earth's atmosphere?

The main components of the Earth's atmosphere are correctly identified as nitrogen, oxygen, argon, carbon dioxide, and trace gases. Nitrogen constitutes about 78% of the atmosphere, making it the most abundant gas, followed by oxygen at approximately 21%. Argon is present in smaller amounts, around 0.93%, and carbon dioxide, while only about 0.04%, plays a critical role in the greenhouse effect and is essential for life due to its involvement in photosynthesis.

Trace gases, including neon, helium, methane, and others, make up only a small fraction of the atmosphere but are important for various atmospheric processes. Understanding these components and their proportions is fundamental to meteorology and climate science.

In contrast, the other selections include gases that are either not present in significant enough quantities to be classified as major components or are not typically found in the atmosphere at all. For example, while helium is a gas found on Earth, it is extremely rare in the atmosphere, and sulfur dioxide, while a pollutant relevant to air quality issues, is not a primary constituent of the atmosphere. Similarly, hydrogen and methane are trace gases that, although important, do not account for the bulk of the atmospheric composition.