All of the following can trigger a cell to release hormones, EXCEPT:?
1) a binding of neurotransmitters released by a presynaptic autonomic neuron
2) b binding of hormones released by a different endocrine cell
3) c binding of neurotransmitters released by a presynaptic somatic neuron
4) d A change in local conditions (e.g., changing pH) in the interstitial fluid surrounding the cell