The best answer is D. The first paragraph states that plant cells “differentiate and form structures” when a “complex system of chemical messengers”activates a “small subset of the genes in a particular kind of cell”. In the passage, the author elaborates on the hormonal system in plants by indicating that the pleiotropic plant hormones activate enzymes, which in turn release oligosaccharins-the “more specific chemical messengers”. The second paragraph indicated these specific chemical messengers have specific effects on plant development. Thus, the passage indicates that it is the oligosaccharins that directly influence the development of a plant cell by controlling the expression of a plant cell’s genes. Choices B and C are incorrect because the oligosaccharins are themselves specific chemical messengers and are not said to produce any hormones. The passage provides no information to support A.