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: Surgery
Best way to diagnose lower small intestine obstruction is 
Select and explain. 
A. Pain abdomen, B. Profuse bilious vomiting, C. Multiple air fluid levels, D. Feculent vomiting
C: Multiple air fluid levels
Answer: C: Multiple air fluid levels 
Explanation: In erect abdominal x-ray of small intestine obstruction, multiple air fluid levels seen.