The ionic compounds and the explanation of the choices are as follows; A. Compounds A and D because they have relatively high melting points.
Why the compounds are selected
Ionic substances readily dissolve in water because the polar water molecules attract the ions, breaking the ionic bonds and surrounding the ions with hydrogen bonds.
When dissolved, these substances carry an electric charge throughout the solution or liquid. This allows ionic solutions and melts to conduct electricity well. Also, they have high melting points. The only compounds that meet these specifications are compounds A and D.