This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Parasympathetic System & Glaucoma, Subject name: Pharmacology
[{'content': 'Which of the following provides the best explanation for neostigmine being preferred over physostigmine for treating myasthenia gravis? \nSelect and explain. \nA. It is better absorbed orally, B. It has longer duration of action, C. It has additional direct agonistic action on nicotinic receptors at the muscle end plate, D. It penetrates blood brain barrier', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Neostigmine is a quaternary ammonium derivative and is water soluble. Its absorption from GIT and penetration in the brain and cornea is much less than physostigmine. It produces additional action on NM receptors.', 'role': 'assistant'}]