This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
[{'content': 'Contraindications of beta blockers are:  a) Asthma b) Heart block  c) Hypertension d) Arrhythmia \nSelect and explain. \nA. b, B. ab, C. c, D. cd', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]