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
The most common cause of acute cor pulmonale is 
Select and explain. 
A. Pneumonia., B. Pulmonary thromboembolism., C. Chronic obstructive pulmonary disease., D. Primary spontaneous pneumothorax.
B: Pulmonary thromboembolism.
Answer: B: Pulmonary thromboembolism. 
Explanation: None