The best answer is D. According to the passage, “The pleiotropy of the five well-studies plant hormones is somewhat analogous to that of certain hormones in animals”. The example given involves certain hypothalamic hormones that “stimulate the anterior lobe of the pituitary gland to synthesize and release many different hormones, one of which stimulates the release of hormones from the adrenal cortex”. These hormones in turn “have specific effects on target organs all over the body”. This “hierarchy of hormones,” as the author calls it, “may also exist in plants”, where the five pleiotropic hormones may “function by activating the enzymes that release … more specific chemical messengers”. Thus, hypothalamic hormones in animals and the five major hormones in plants occupy a similar place in the respective organisms” hormonal hierarchy.