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
True about osteoporosis 
Select and explain. 
A. Normal serum calcium levels, B. Normal serum phosphate levels, C. Normal serum alkaline phosphatase level, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: None