Answer : Option A) 0.5 M NaCl.
Explanation : A solution can be called as a stronger electrolyte which when dissolved in aqueous solution and produce ions in the solutions and is easily decomposed by electrolysis. Amongst the given options NaCl produces Na ions and Cl ions on dissolving with water rest all are not so readily soluble in water. As only salts which belong to Group I elements are soluble electrolytes.