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: Pathology
[{'content': 'Sudden death, right sided heart failure (cor pulmonale or cardiovascular collapse) occur when - \nSelect and explain. \nA. Small pulmonary embolism, B. Massive pulmonary embolism, C. 60% or more of pulmonary artery is obstructed with emboli, D. End artery obliteration', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]