Here's a problem to solve: Which of the following describes the mechanical energy of a cart at rest at the top of a steep hill?

Among the 4 following options, which is the correct answer?

- A: The cart has no mechanical energy.
 
- B: The cart's mechanical energy is all kinetic.
 
- C: The cart's mechanical energy is all potential.
 
- D: The cart's mechanical energy is half potential and half kinetic.
 