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: 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: Ans. Digital subtraction angiography