Carbon Dioxide/Carbon Monoxide?

The thing that makes carbon monoxide poison is the shape of the molecule. In biological reactions, often a molecule will fit into a certain shape of receptor on a cell - one that was made for a molecule with a similar shape. The receptor gets confused by the similarities and lets the wrong molecule in. Carbon dioxide, although chemically close, have a vastly different shape.

In either case, the oxygen is bonded to the carbon and does not unbond.

Both are poisons, but work by different mechanisms. With CO2, a person suffocates because the CO2 does not provide any oxygen. However, in a gas mix with air, it takes a pretty high concentration of CO2 for this to happen, something like several percent in air.

CO is sneakier, because it can coordinately bond with hemoglobin, which is a fancy metal complex that ordinarily transports oxygen in the bloodstream. CO forms a stronger bond with hemoglobin, so the CO is preferentially transported into the body with hemoglobin. The more CO there is, the less oxygen bonds to hemoglobin, and a person suffocates due to oxygen deprivation. The CO concentration in air which would cause death is much lower.

because your lungs exhale carbon dioxide (idk why they have to).

The oxygen in your blood in your lungs goes and bonds with the carbon of Carbon Monoxide and thus you lose oxygen from your blood when inhaling CO. CO has a similar effect to suffocation if i remember right.

2CO + O2 ----> 2CO2

No....those are not my options....they are your options.... Now go do your own homework!!