About 21% of the Earth's atmosphere is composed of oxygen.
About 21 of the Earth's atmosphere is made up of oxygen.
Earth's atmosphere is about 21% oxygen by volume (for dry air).
Oxygen makes up about 21% of Earth's atmosphere.
The percentage of oxygen in the Earth's atmosphere by mass is approximately 21.
About 21% of the Earth's atmosphere is oxygen.
Oxygen forms 21 percent of the Earth's atmosphere.
The oxygen in Earth's atmosphere has been generated, over geological time, by the plant life on Earth.
No, nitrogen does not dilute the oxygen in Earth's atmosphere. Nitrogen and oxygen are the two main components of Earth's atmosphere, with nitrogen making up about 78% and oxygen about 21%. They coexist in the atmosphere without one diluting the other.
The most abundant gases are nitrogen and oxygen in the Earth atmosphere.
Oxygen is the gas that makes up about 21 percent of the Earth's atmosphere.
Oxygen is the primary component, making up about 21% of Earth's atmosphere.