What is air primarily composed of?

Air is primarily composed of gases, with nitrogen making up about 78% of its composition, oxygen about 21%, and the remaining 1% consisting of other gases such as argon and carbon dioxide. This combination of gases is crucial for sustaining life on Earth, as oxygen is essential for respiration in animals and plants, while carbon dioxide is important for photosynthesis in plants.

Option B accurately reflects this composition, highlighting the key components of air – nitrogen, oxygen, carbon dioxide, and argon. The inclusion of all these gases shows a broader understanding of the atmospheric mixture than alternatives that focus too narrowly on just a few components.

In contrast, other options lack the comprehensive view necessary to describe the actual composition of air effectively. Some options mention only two gases or exclude significant components such as argon and carbon dioxide, which are present in the atmosphere, albeit in smaller quantities. This makes the correct choice the most informative regarding what constitutes the air we breathe.