Urea is a waste product primarily produced from the breakdown of:

Urea is a waste product that is primarily produced from the breakdown of amino acids. When proteins are metabolized in the body, amino acids are released. These amino acids can be further deaminated, a process that removes the nitrogen-containing amino group (NH2). This nitrogen is then converted into urea in the liver through the urea cycle. The formation of urea allows for the safe excretion of excess nitrogen from the body, as high levels of ammonia, the byproduct of amino acid deamination, can be toxic. Therefore, the primary source of urea production is indeed the breakdown of amino acids, which makes this answer correct.

The other choices involve substances that are not the primary source of urea. Carbohydrates and fats primarily metabolize into glucose and fatty acids, respectively, which do not produce urea. Nucleic acids are broken down into nucleotides, which also do not contribute significantly to urea production. Thus, focusing on amino acids reveals the critical link to urea synthesis in the body.