This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous system, Subject name: Physiology
[{'content': 'Acetylcholine acting on nicotinic receptors produces \nSelect and explain. \nA. Contraction of skeletal muscle, B. Secretion saliva, C. Bradycardia, D. Pupillary constriction', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Acetylcholine acting at motor and causes muscle contraction Ref: guyton and hall textbook of medical physiology 12 edition page number:76,77,78', 'role': 'assistant'}]