Conductivity of Ionic Compounds in Solution

A student is investigating the solubility of various ionic compounds in water. They prepare saturated solutions of the compounds listed below:

- Potassium chloride (KCl)

- Sodium sulfate (Na₂SO₄)

- Barium hydroxide (Ba(OH)₂)

- Calcium carbonate (CaCO₃)

After thorough mixing, the student measures the electrical conductivity of each solution using a conductivity meter.

Which of the following compounds would be expected to exhibit the highest conductivity in solution?