Final answer:
Proteins, bicarbonate, and carbonic acid are common participants in the regulation of body fluid pH. Oxalic acid is not involved in this process.
Step-by-step explanation:
In the regulation of body fluid pH, all of the following are common participants: proteins, oxalic acid, bicarbonate, and carbonic acid.
Proteins are important buffers in the body, helping to maintain pH balance in biological systems. Bicarbonate ions and carbonic acid are part of the bicarbonate buffer system, which is the primary buffering system in the body's interstitial fluid (IF) surrounding the cells. This system helps resist changes in pH.
Oxalic acid is not a common participant in the regulation of body fluid pH.