The correct option is B Ammonia
Breakdown of proteins produce amino acids. During degradation of amino acids, amino acids are deaminated and released as nitrogenous waste. These nitrogenous wastes can be eliminated in the form of ammonia, urea and uric acid.
Among these nitrogenous wastes, ammonia is the most toxic form of nitrogenous waste. Ammonia requires large amounts of water for its elimination. Hence, only some organisms like bony fishes, aquatic amphibians and aquatic insects excrete ammonia. Such organisms are known as ammonotelic.
The decreasing order of toxicity of these excretory products is:
Ammonia > Urea > Uric acid