The answer is A) they provide a source of energy.
I believe the correct answer would be the parathyroid hormone (PTH) and calcitonin. Both of this hormones work in hand in hand in regulating the phosphate and the calcium levels present in the blood. Hope this answers the question.
Answer:
Made mostly of collagen, bone is living, growing tissue. Collagen is a protein that provides a soft framework, and calcium phosphate is a mineral that adds strength and hardens the framework. This combination of collagen and calcium makes bone strong and flexible enough to withstand stress.
Explanation: