( A ) Some amount of urea may be retained in the kidney matrix of some of ureotelic animals to maintain a desired osmolarity.
( B ) Ammonia produced by metabolism is converted into urea in the kidney of ureotelic animals and released into the blood which is filtered and excreted out by the kidneys
( C ) The process of excreting ammonia is Ammonotelism. Eg. bony fishes, aquatic amphibians and aquatic insects
( D ) Mammals, many terrestrial amphibians and marine fishes mainly excrete urea and are called ureotelic animals.