the sum of the potential and kinetic energy the difference of the potential and kinetic energy only the kinetic energy only the potential energy
I gave my students this multiple choice question: What does the mechanical energy of a system include?

Only one answer is correct among these 4 choices:
- the sum of the potential and kinetic energy
- the difference of the potential and kinetic energy
- only the kinetic energy
- only the potential energy

Could you tell me which one is correct?

the sum of the potential and kinetic energy