An organic compound containing only carbon, hydrogen, and oxygen could be a carbohydrate, but it could not be a protein.
Carbohydrates are organic compounds that contain carbon, hydrogen, and oxygen in a 1:2:1 ratio, with the general formula (CH2O)n. They are the primary source of energy for living organisms and include sugars, starches, and cellulose. Therefore, any organic compound with this chemical composition could potentially be a carbohydrate.
Proteins, on the other hand, are composed of amino acids, which contain nitrogen in addition to carbon, hydrogen, and oxygen. While some amino acids do contain oxygen, no protein can be composed solely of carbon, hydrogen, and oxygen. Therefore, an organic compound containing only these three elements could not be a protein.