What do you breathe in and what do you breathe out?

Answer 1

Oxygen in, Carbon Dioxide out.

Another answer

Breathing breathes in the atmosphere: not the whole atmosphere obviously, but its composition. Breathing in occurs because of the necessity of oxygen-entrance and breathing out occurs because of the necessity of carbon dioxide-exit.

The air consists of 79% nitrogen and 21% oxygen and 0.04% carbon dioxide and equally tiny percentages of other gases. We breathe in this 79% nitrogen and breathe out an equal percentage. We breathe in 21% oxygen and breathe out 16% oxygen. We breathe in 0.04% carbon dioxide and breathe out 4-5% carbon dioxide.

Answer 2

you brethe in everything in the air but your lungs filter out the bad stuff and keep the oxygen and everything else is brethed out

Answer 3

air

Answer 4

Oxygen and carbon dioxide