Chemosynthesis of self replicating nucleic acids and proteins followed by aggregation of proteins around nucleic acid resulted in origin of first life form. Also known as protovirus, eobiont or protocell, the first life forms were nucleoproteins that lack chlorophyll i.e. they were non-green. The organic molecules (as formed by polymerization and condensation of primitive gases in sea) served as source of carbon and energy source for first living forms of the earth. Since they used organic compounds as their carbon and energy source, the first life forms were chemoheterotrophs. Absence of molecular oxygen allowed only anaerobic fermentation of organic compounds to release energy; the first life forms were anaerobic. This makes Assertion a correct statement. Due to limited supply of organic compounds, organisms evolved into chemoautotrophs that use the energy released by decomposition of inorganic compounds to form organic compounds. Since the source of electrons is an inorganic/organic molecule such as hydrogen sulphide; oxygen is not formed and the process is termed as non oxygenic photosynthesis. This makes Reason correct but the reason is not the correct explanation for assertion. Thus, the correct answer is B.