Showing that energy of a falling object remains constant

[MadmanMurray]

I got this question on a sample test but I don't know how they want me to answer it
Q.) Show that for a falling body, the total amount of energy is constant at any point
I suppose I could state the potential energy then draw a graph of how the potential energy is converted into velocity. Is that what they mean?

 

[rl.bhat]

Consider the starting point, end point and anyone point in between them. Then find potential energy, kinetic energy at these point and find the total energy. Show the it remains constant.