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': 'Which among the following is an early sign of magnesium toxicity ? \nSelect and explain. \nA. Depression of deep tendon reflexes, B. Respiratory depression, C. Cardiac arrest, D. Decreased urine output', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]