Answer:
Out of K(Potassium), Cl(Chlorine) and Mg(Magnesium) the ion most similar to the ion responsible for trigger for muscles based on its periodic table position is Mg(Magnesium).
Explanation:
Calcium ions are responsible for triggering muscles contraction cycle in the body which binds to troponin (a protein complex of three proteins integral to muscle contraction).
Since, calcium and magnesium belongs to the same block in the periodic table, they have similar chemical properties. So, it is correct to say that Magnesium (Mg) is the most similar ion trigger for muscles activity.