Oxygen accounts for approximately what percentage of the air we breathe?

Oxygen accounts for approximately what percentage of the air we breathe?

• A. About 20%
• B. About 50%
• C. About 1%
• D. About 80%

Answer: (A)

Air is a mixture of gases, and oxygen makes up about one-fifth of that mix. In dry air, roughly 78% is nitrogen, about 21% is oxygen, and the rest are trace gases. So oxygen is about 20% of what we breathe, which is why this option is the best choice. The other numbers don’t fit because they would imply much more or much less oxygen than is actually present in ambient air.

Air is a mixture of gases, and oxygen makes up about one-fifth of that mix. In dry air, roughly 78% is nitrogen, about 21% is oxygen, and the rest are trace gases. So oxygen is about 20% of what we breathe, which is why this option is the best choice. The other numbers don’t fit because they would imply much more or much less oxygen than is actually present in ambient air.