This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diseases of orbit, Lids and lacrimal apparatus, Subject name: Ophthalmology
A young adult presents with proptosis and pain in eye after 4 days of trauma to eye. Chemosis, conjunctival congestion and extraocular muscle palsy with inability to move eye are seen. Investigation of choice - 
Select and explain. 
A. MRI, B. Digital subtraction angiography, C. CT, D. MR angiography
B: Digital subtraction angiography
Answer: B: Digital subtraction angiography 
Explanation: Digital subtraction angiography is the investigation of choice in this case,Digital subtraction angiography (DSA) is a fluoroscopy technique used in interventional radiology to clearly visualize blood vessels in a bony or dense soft tissue environment