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
A post-operative cardiac surgical patient developed sudden hypotension, raised central venous pressure, pulsus paradoxus at the 4th post operative hour. The most probable diagnosis is: 
Select and explain. 
A. Excessive mediastinal bleeding, B. Ventricular dysfunction, C. Congestive cardiac failure, D. Cardiac tamponade
D: Cardiac tamponade
Answer: D: Cardiac tamponade 
Explanation: Answer is D (Cardiac tamponade) Features of rising pressure, falling aerial pressure and pulsus paradoxus following surgery on the hea leads us to the diagnosis of cardiac tamponade.