What electrolyte inactivates troponin and allows actin and myosin to form a bridge enabling fibers to contract?

Choice A rationaleMagnesium plays a role in various cellular functions, including enzyme activity and muscle contraction, but it does not directly inactivate troponin to enable actin and myosin interaction.Choice B rationaleSodium is essential for action potential generation and nerve impulse transmission but does not directly influence troponin activity or muscle contraction through actin and myosin bridge formation.Choice C rationalePotassium is critical for maintaining cellular resting membrane potential and repolarization of cells but does not play a direct role in inactivating troponin to facilitate muscle contraction.Choice D rationaleCalcium is the electrolyte that inactivates troponin, allowing actin and myosin to form cross-bridges and contract muscle fibers. Calcium binds to troponin, causing a conformational change that exposes binding sites for myosin on actin filaments.