Hint: Snakes are the members of the superclass Tetrapoda. They belong to the phylum Chordata or Vertebrata. They are further a member of the class Reptilia. Further, they belong to the subclass Diapsida and order Squamata.
Complete answer: Snakes belong to the suborder Ophiura. Snakes are characterized by the absence of limbs, and the presence of a vestigial pectoral, and the pelvic girdle. These are their evolutionary characters. For excretion, they have a metanephric kidney. These organisms excrete nitrogenous wastes in the form of uric acid. They excrete out the pellets or the paste of uric acid with minimum loss of wastes. Uric acid is insoluble in water. It is done to conserve the water as the excretion of urea requires high quantities of water. Therefore, uric acid helps in conserving the water.
Examples – reptiles, birds, land snails, and insects.
a) Ureotelic – These are organisms that excrete nitrogenous wastes as urea. Urea is soluble in water; therefore, the excretion of urea requires large quantities of water. However, it is very less toxic as compared to Uric acid.
Examples – mammals, terrestrial amphibians, and marine fishes.
b) Ammonotelic – These organisms excrete nitrogenous wastes as ammonia. Ammonia is highly toxic and the excretion of ammonia requires large quantities of water. It is generally excreted by diffusion from the body surfaces. Moreover, kidneys do not play any significant role in the excretion of ammonia.
Examples – Bony fishes, aquatic amphibians, aquatic insects, aquatic invertebrates like Amoeba, Hydra, sponge, starfish, crayfish, etc.
Hence, the correct answer is option A.
Note: The kidney is formed by the mesoderm of the embryo. The mesoderm forms three chambers that are known as the three soma or nephrostomes. Based on the functional soma, the kidney is classified into three types.
a) Pronephric kidney – The upper or the first soma is functional. It has no nephrons and the funnels are ciliated.
b) Mesonephric kidney – The middle soma is functional. It has less developed nephrons.
c) Metanephric kidney – The last or the lower soma is functional. It has well-developed nephrons.