The compound that will conduct electricity when dissolved in water is CuSO4 (copper(II) sulfate). This is because CuSO4 is an ionic compound, and when dissolved in water, it dissociates into Cu²⁺ and SO₄²⁻ ions, which are charged particles that carry electrical current. In contrast, CH4 (methane) and C (carbon) are molecular or elemental substances that do not produce ions in water and therefore do not conduct electricity when dissolved. Thus, among the given options, CuSO4 will conduct electricity in an aqueous solution by virtue of its ionic nature and ion dissociation in water.