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: Dental
The source of calcium ions of a calcific bridge in a
tooth in which calcium hydroxide pulpotomy has been
performed is: 
Select and explain. 
A. Blood vessel borne, B. Derided cells, C. Dentin, D. From the calcium hydroxide
A: Blood vessel borne
Answer: A: Blood vessel borne 
Explanation: None