Final answer:
Calcium and phosphorus share a synergistic relationship affecting each other's concentrations in plasma and are vital in bone formation through a synthesis reaction. The option (A) is correct.
Step-by-step explanation:
Calcium and phosphorus have a synergistic relationship, where the presence of one can significantly affect the levels of the other. In plasma, a reciprocal relationship exists between the concentrations of calcium and phosphate ions. This indicates that an increase in serum phosphate can cause a fall in serum calcium concentration.
The relationship of calcium and phosphorus is crucial, particularly in the formation of bone. When calcium, phosphorus, and other elements bond together, they form mineral crystals that are a critical structural component of bone. This process is known as a synthesis reaction. Therefore, option (A) is correct.