Which of the following substances is NOT produced from the decomposition of proteins?

The correct answer is carbon monoxide, as it is not a direct product of protein decomposition. When proteins undergo decomposition, they break down into simpler compounds through processes such as putrefaction. This process primarily produces nitrogenous compounds including amino acids, urea, and gases like carbon dioxide.

Amino acids are released due to the hydrolysis of proteins, while urea is produced as a product of amino acid catabolism, particularly through the urea cycle, which helps eliminate excess nitrogen from the body. Carbon dioxide is a natural byproduct of cellular respiration and decomposition processes, as organic matter breaks down.

On the other hand, carbon monoxide is typically associated with incomplete combustion processes rather than the breakdown of proteins. It does not form as a direct result of protein decomposition, making it the correct answer in this context.