Which of the following elements makes up the smallest percentage of the atmosphere?

A. Oxygen

B. Nitrogen

C. Carbon dioxide

c: Carbon Dioxide

Explanation:

Earth's atmosphere is mainly made up of:

78% nitrogen

21% oxygen

0.03% carbon dioxide

And smaller percentages of other elements. Therefore, out of the options, the answer is carbon dioxide

Answer: A

Explanation:

Oxygen makes up another 20 to 21 percent of our atmosphere. It's essential for life on Earth, and interestingly enough, it is poisonous when highly concentrated. Our concentration of 20 to 21 percent seems just right.