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: Radiology
Defenitive test to diagnose pulmonary embolism 
Select and explain. 
A. V/Q Scan, B. Chest X-ray, C. CT pulmo angrography, D. MRI
C: CT pulmo angrography
Answer: C: CT pulmo angrography 
Explanation: CTPA is defenitive test or gold standard test.