The best answer is D) Living matter would be created from reproducing molecules.
Since the reproduction of organic molecules is generally considered to be the precursor to life on Earth, the scientists would design an experiment to replicate this.
Plants were not created from rocks, and fossils indicate previous life, so they would not have been present for life's origin. C is tempting, but genetic code came from the evolution of life, and thus could not be an 'ingredient" for life's origin.
