(easy, 50 points! ) us humans breathe (a oxygen (b carbon dioxide (c carbon monoxide (d nothing

A becuaase you breathe in oxygen and you release carbon dioxide.

We breathe in a mixture of the first two actually. The air is composed of 78% nitrogen, 21% oxygen, 0.03% carbon dioxide and 0.07% of other gases. Technically, you can also breathe in carbon monoxide if it is present within your environment. However, it has harmful effects. It can enter your bloodstream and mix with hemoglobin to form carboxyhemoglobin. The blood cannot carry oxygen anymore, and this causes the body's cells and tissue to die.

Its either c or d. i would go with d though, because im not sure if its legal in all of the us

Grade point average. it's literally in the name