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: Physiology
Role of calcitonin is: 
Select and explain. 
A. Lower Ca level, B. Increase Ca level, C. Decrease PO4, D. None of the above
A: Lower Ca level
Answer: A: Lower Ca level 
Explanation: Lower Ca level