3) which of the following is (are) true? a) hormones regulate cellular functions, and generally

3) which of the following is (are) true? a) hormones regulate cellular functions, and generally negative feedback regulates hormone levels. b) the circulating level of a hormone is held constant through a series of positive feedback loops. c) both lipid-soluble hormones and water-soluble hormones bind to intracellular protein receptors. d) the ducts of endocrine organs release their contents into the bloodstream. e) only a and c are true.