What is the composition of air primarily made up of?

The primary composition of air is best represented by the first choice, which specifies that air is made up of approximately 78% nitrogen, 21% oxygen, and 1% other gases. This composition reflects the typical atmospheric conditions found at sea level, where nitrogen is the most abundant gas, followed by oxygen, with other trace gases like argon, carbon dioxide, and varying amounts of water vapor making up the remainder.

The accuracy of this answer is supported by extensive scientific studies and standards in atmospheric science. It captures the essential components necessary for various processes on Earth, such as combustion, respiration, and plant photosynthesis. Understanding this typical composition is crucial for fields like aviation, meteorology, and environmental science, as it affects air density, atmospheric pressure, and the behavior of weather systems.

In contrast, other options fail to represent the true composition of the atmosphere accurately. For instance, stating that air is composed of 100% oxygen is misleading, as such an environment would be uninhabitable for most life forms and is not reflective of natural air. Similarly, claiming that air consists of 50% carbon dioxide and 50% nitrogen does not align with atmospheric science data, since carbon dioxide is present only in trace amounts under normal conditions