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
Investigation of choice for pulmonary embolism 
Select and explain. 
A. CT scan, B. Contrast CT, C. Ventillation - Perfusion Scan, D. MRI
B: Contrast CT
Answer: B: Contrast CT 
Explanation: B i.e. Contrast CT