NO FAKE ANSWERS AND NO LINKS. How much oxygen does the atmosphere contain?

21%

Explanation:

To remember this percentage, use the amount of land and water on earth, like this: 3 (land) x 7 (water) = 21

(note: oxygen does not change depending on land or water amount)

The air in Earth's atmosphere is made up of approximately 78 percent nitrogen and 21 percent oxygen.

Explanation:

hope this helps

plz mark brainliest

answer; i believe the correct answer is (replication is not conservative);

thrombocytopenia, which is a deficiency in blood platelets, can cause bleeding and bruising in the dermis similar to senile purpura. other possible causes include: exposure to ultraviolet rays and aging skin are common causes of senile purpura. senile purpura may also be a sign of collagen loss in the skin and bones.