Unlike the oligosaccharins（寡聚糖素）, the five well-known plant hormones are pleiotropic rather than specific; that is, each has more than one effect on the growth and development of plants.请根据上下文猜一猜，pleiotropic的词义是什么？A:破坏性 B: 单一性 C:无效性 D:多效性 答案: 多效性