4. Testosterone is a lipophilic steroid hormone that diffuses freely across the plasma membrane of all cells via passive diffusion. Despite this ubiquitous entry, only specific "target cells" exhibit a physiological response. Which statement best explains this specificity?
(A) All cells possess the gene for the testosterone receptor, but only target cells have undergone the epigenetic modifications necessary to express the receptor protein.
(B) Targeted response is determined by the presence of cell-surface protein channels that actively pump testosterone into the cytoplasm against its concentration gradient.
(C) Only target cells possess the membrane-bound G-protein coupled receptors (GPCRs) required to activate the adenylyl cyclase signaling pathway.
(D) The high concentration of cytoplasmic proteases in non-target cells degrades testosterone before it can reach the nuclear envelope.
(E) Only target cells contain the specific intracellular receptor proteins that, upon ligand binding, translocate to the nucleus to act as transcription factors.