The correct option is D Molecules of organic compounds
The heterotrophic hypothesis, also known as the Haldane-Oparin hypothesis after two scientists who independently proposed it, posits that life (organic molecules) could have formed from inorganic molecules. In other words, life could have formed without requiring a 'divine nudge' and without having to come from another planet. Much research has been conducted to explain how life could spontaneously form. The general theme is that components of earth's atmosphere could form into complex organic molecules, which could then assemble into more complex groupings, which eventually would become life. So, According to heterotroph hypothesis, the source of food for the earliest form of life consisted of molecules of organic compounds. Thus, option D is correct and other options are wrong.