The hormone epinephrine causes opposite effects in two populations of target cells because _____.
a. epinephrine can only reach target cells in adipose tissue, as it is fat-soluble
b. epinephrine activates biochemical pathways in one set of target cells but works only by changing gene expression in the other set of target cells
c. epinephrine crosses the membrane on one set of target cells but binds to membrane-bound receptors in the other set of target cells
d. the chemical form of epinephrine released by neurons is different from the epinephrine released by endocrine cells
e. each set of target cells has different receptor-transduction mechanism