Which type of acetylcholine receptor is present on postganglionic neurons

Mescarinic and Nicotinic

Explanation:

Postganglionic fibers can be present in both sympathetic and parasympathetic divisions, their main difference resides in how in the sympathetic division the postganglionic fibers are adrenergic and use norepinephrine (noradrenalin) as a neurotransmitter, in the parasympathetic division, on the other hand, fibers are cholinergic and use acetylcholine as a neurotransmitter, the postganglionic neurons of sweat glands release acetylcholine for the activation of muscarinic receptors, another kind of receptor for acetylcholine are nicotinic receptors that act as transmembrane sodium/potassium channels, while muscarinic receptors need to act through intracellular proteins.

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c. because step up transformer steps up the input voltage i.e increases the input voltage  

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increased stability in the completion of fluorine's outer shell.