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': 'Glucagon is most effective for which of the following conditions ? \nSelect and explain. \nA. Cocaine intake with BP of 180/110 mmHg, B. Old man with decreased BP/decreased heart rate due to atenolol, C. Old man with type 2 diabetes mellitus and no glipizide for 4 days, D. Female with lactic acidosis due to shock', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]