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: Unknown
First Investigation of choice in blunt trauma abdomen when the patient first comes to the ER room- 
Select and explain. 
A. CT, B. MRI, C. X-ray abdomen, D. FAST
D: FAST
Answer: D: FAST 
Explanation: Ans. is 'd' i.e., FAST