Life originated as a fairly complex organism in simple surrounding is conclusion of

The Heterotroph hypothesis is the proposal that the first living organism was a heterotroph. Heterotrophs are organisms that obtain their energy by feeding on others (or on organic compounds). Before there were other organisms, they would feed on surrounding left-overs of their origin. The simplest process we know of today by which organisms do this is called fermentation. There is evidence that the pre-life atmosphere and water environment was a reducing one, (no oxygen).
Evidence: There are no iron oxides (rust-red rocks) in unexposed deposits of that age.
The waste products of Fermentation are ethyl alcohol (ethanol) and carbon dioxide (CO${}_2$). Thus, option B is correct.
The autotrophic hypothesis states that the first living beings on Earth were producers of their own food. Thus, option A is wrong.
Biogenesis is the production of new living organisms or organelles. The law of biogenesis, attributed to Louis Pasteur, is the observation that living things come only from other living things, by reproduction (e.g., a spider lays eggs, which develop into spiders). Thus, option C is wrong.
Abiogenesis is the process by which a living organism arises naturally from non-living matter, as opposed to biogenesis, which is the creation of living organisms by other living organisms. Thus, option D is wrong.