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: Orthopaedics
Which of the changes occur in bone growth - 
Select and explain. 
A. Increased acid phosphatase, B. Increased urinary calcium, C. Increased bone nucleotidase, D. Increased osteocalcin
D: Increased osteocalcin
Answer: D: Increased osteocalcin 
Explanation: During bone growth and development, bone formation, i.e. osteoblastic activity predominates → Osteocalcin is used as sensitive and specific serum marker for osteoblastic activity.