Which compounds were formed in direction of origin of life?

Amino acids were formed by condensation, polymerization and redox reactions of hydrocarbons, ammonia and water in primitive ocean under influence of energy from UV rays, radiations and lightening. RNA catalyzed polymerization of these amino acids formed polypeptides. Formation of amino acids and proteins was common to all type of organisms as these components serve fundamental structural and functional role. This makes options B, C and D incorrect. Nucleic acids were formed in primitive hot soup of sea by formation of pyrimidine-sugar ?phosphate and purine-sugar-phosphate. RNA has ability of self replication and to catalyze other chemical reactions. Thus, RNA served as enzyme as well as genetic material in first life forms. Though, both RNA and protein had catalytic activities, RNA extended its functions to self replication while proteins continued to serve as enzymes. Switching from RNA to DNA, as a genetic material, was favoured later due to less susceptibility of double stranded DNA molecules to breakage and mutations as compared to that of single stranded RNA. Error prone replication of single stranded RNA provided raw material for evolution of different organisms from primitive organisms. The early aquatic life forms produced water soluble ammonia as their excretory product which was diffused out of body surface by simple diffusion. Transition of life from water to land posed a need for production of less toxic excretory product to conserve water and led to evolution of pathway that convert ammonia into less toxic urea which is filtered and excreted out by kidneys; examples: mammals, terrestrial amphibians and marine fishes. This makes option A correct as both urea and nucleic acid evolved with increasing complexity of life forms.