The contents of two sealed containers are sketched below.
• Container A (1.0 L) holds 10 blue spheres labeled "Na⁺," 10 red spheres labeled "Cl⁻," and many water molecules.
• Container B (1.0 L) holds 5 intact linear molecules labeled "CO₂" dispersed among many water molecules.
Identify which container holds an electrolyte solution and justify your choice in one or two sentences.