Concept: This question tests your understanding of the neurotransmitters associated with the autonomic nervous system, specifically the parasympathetic division.

Why (B) is correct: The parasympathetic nervous system primarily releases acetylcholine as its neurotransmitter at both preganglionic and postganglionic nerve endings. Acetylcholine acts on muscarinic and nicotinic receptors to produce its characteristic 'rest and digest' effects.

Why other options are wrong:

• (A) Serotonin: Serotonin is a neurotransmitter involved in mood, sleep, and digestion, but it is not the primary neurotransmitter of the parasympathetic nervous system.
• (C) Epinephrine: Epinephrine (adrenaline) is a hormone released by the adrenal medulla and also acts as a neurotransmitter in the sympathetic nervous system, not the parasympathetic.
• (D) Norepinephrine: Norepinephrine (noradrenaline) is the primary neurotransmitter released by most postganglionic neurons of the sympathetic nervous system.

Common Mistake: Students often confuse the neurotransmitters of the sympathetic and parasympathetic nervous systems. Remember that acetylcholine is the key player for 'rest and digest'.

NEET Tip / Mnemonic: Think of 'Parasympathetic = Acetylcholine' (PA). For sympathetic, remember 'Sympathetic = Norepinephrine/Epinephrine' (SNE).

Correct Answer: (B)