Electrical conductivity of an aqueous solution is based on ions present in the water. Pure, deionized water does not effectively conduct electricity. The more ions that are present in the water, the better the solution will conduct electricity. So salts that ionize completely will have a higher conductivity than salts that do not ionize completely. KCl completely ionizes in water. So does HNO3. As a strong acid, it completely ionizes into protons (H+) and nitrate ions (NO3-). So HNO3 would have a similar conductivity to KCl. BaO does not ionize completely in water, so it would have a lower conductivity than the other two.