Which lists all of the substances that appear in equilibrium constant expressions?

Below are the choices that can be found from other sources:

pure gas and pure liquid
pure gas and aqueous solution
pure solid and pure liquid
aqueous solution and pure liquid

the answer is it could be pure solid and pure liquid but not sure

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.