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 8 year old boy is being treated for rickets. Which of the following investigations shows the earliest evidence for healing? 
Select and explain. 
A. Serum Ca, B. Serum phosphates, C. Radiological examination of long bones, D. Serum ALP
C: Radiological examination of long bones
Answer: C: Radiological examination of long bones 
Explanation: The earliest feature of healing in rickets is seen in X ray of growing end of the bones.