28. Testosterone is an example of a chemical signal that affects the very cells that synthesize it, the neighboring cells in the testis, along with distant cells outside the gonads. Thus, testosterone is an example of _________.
I) an autocrine signal
II) a paracrine signal
III) an endocrine signal (A) only I and II (B) only II and III (C) only I and III (D) I, II, and III