Answer:
Calcium
Step-by-step explanation:
Calcium is an important element present in the organisms body. The calcium can acts as an important messenger molecule and helps in the process of muscle contraction.
The concentration of calcium ions in the myoplasm leads to the development of force necessary for the movement of actin and myosin molecule. The calcium ions cling the cross bridge formation during muscle contraction.
Thus, the correct answer is option (b).