Question

78% of the earths atmosphere is ________ and 21% of the earths atmosphere is ________.
1 oxygen, nitrogen
2 nitrogen, oxygen
3 nitrogen, carbon dioxide
4 oxygen, carbon dioxide

Explanation:

To solve this, we recall the composition of Earth's atmosphere: approximately 78% is Nitrogen and 21% is Oxygen. We then match this with the options. Option 2 (Nitrogen, Oxygen) aligns with this scientific fact.

Answer:

1. Nitrogen, Oxygen