Expiration (breathing out) is how the body removes excessive carbon dioxide from the blood. this is an example of

I think that this is an example of excretion of metabolic waste. Metabolic waste are substances that have been left after metabolism that the body cannot make use of and have to removed from the body. Body excretes are in form of water solute except for carbon dioxide which is in form of gas together with water vapor from the lungs.

The answer would be c