This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
[{'content': 'Which of the following is an effect of acetylcholine? \nSelect and explain. \nA. Relaxes LES, B. Contracts LES, C. Constricts the blood vessels, D. Relaxes the bronchial muscles', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Acetyl choline is a neurotransmitter ,which is a chemical released by nerve cell ir neuron .acetyl choline causes muscle to contract,activate pain responses and regulates endocrine and REM sleep functions Ref:Guyton and Hall textbook of medical physiology 12th edition,page number:77,78', 'role': 'assistant'}]