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
A 14 year old obese child is referred from an endocrinologist for painful limping of hip.Which of the following investigation is least useful in this clinical setting? 
Select and explain. 
A. CT, B. USG, C. MRI, D. X-ray PBH
B: USG
Answer: B: USG 
Explanation: Ans. USG