Answer: a. a cascade effect.
Explanation:
Hormones are the chemicals which are secreted by the glands and tissues of the body. These hormones are transferred into the circulatory system of the body where they are targeted to the tissues for regulating their actions. Some hormones regulate the secretion of other hormones in the body this is called as cascade effect. This cascading effect can be seen at the enzymatic level the activation of one enzyme causes the activation of other enzymes regulated by the hormonal control.