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 patient in ICU has normal pulmonary A pressure; low systemic peripheral resistance; low cardiac index; arterial PO2 = 93; diagnostic possibilities are - 
Select and explain. 
A. Cardiogenic shock, B. Septic shock, C. Cardiac tamponade, D. ATN
C: Cardiac tamponade
Answer: C: Cardiac tamponade 
Explanation: None