This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Angiography, Subject name: Radiology
Gold Standard investigation for pulmonary Thromboembolism? 
Select and explain. 
A. V/Q SCAN, B. CECT, C. Angiography, D. MRI
C: Angiography
Answer: C: Angiography 
Explanation: *Gold standard is Pulmonary Angiography. *IOC - CT Angio. CE pulmonary angiogram showing hypodense thrombus in left main pulmonary aery.