Final answer:
The preganglionic neurons of the sympathetic division primarily release the neurotransmitter acetylcholine.
Step-by-step explanation:
The main neurotransmitter released by the preganglionic neurons of the sympathetic division is acetylcholine (c). This neurotransmitter is vital for transmitting signals from the nervous system to the muscles and for various functions in the autonomic system. In contrast, it is the postganglionic sympathetic neurons that typically release norepinephrine to affect the target organ. However, the preganglionic sympathetic neurons use acetylcholine to communicate with the postganglionic neurons.