The correct option is A Amino acids
Miller and Urey provided first proof for chemical synthesis of proteins by amino acids. They simulated the primitive earth conditions as proposed by Oparin and synthesized simple organic compounds (amino acids, fatty acids sugars etc) from a mixture of methane, hydrogen, water vapour and ammonia. As in primitive atmosphere, hydrogen served as reducing agent while methane provided hydrocarbon skeleton for synthesis of organic compounds. Water served as medium for chemical synthesis of organic compounds in the glass chamber. Thus, the correct answer is option A.