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: Medicine
[{'content': "Which one of the following is indicative of cardiac tamponade? \nSelect and explain. \nA. Pulsus paradoxus, B. Wide pulse pressure, C. Kussmaul's sign, D. Forceful apical. impulse", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]