The correct answer is urea.
Urea is formed from the deamination (removal of amine group) of amino acids producing a highly toxic ammonia. Ammonia will then join carbamyl phosphate to form citrulline. Citrulline will then cycle through the urea cycle until it forms arginine. Arginine then will be broken down to ornithine and urea. Urea is excreted in the urine and ornithine is used to replenish citrulline.
