The best answer is C. The passage states that because each pleiotropic hormone has so many different effects on a plant, pleiotropic hormones “are not very useful in artificially controlling the growth of crops”. In contrast, the passage indicates that oligosaccharins have specific effects on the growth and development of plants. Thus, in comparison to the pleiotropic hormones, oligosaccharins could potentially be effective in artificially controlling specific aspects of crop development. Choices A, B and D can be eliminated because they describe functions that are not attributed in the passage either to the pleiotropic hormones or to oligosaccharins.