Fact 1: Folding an object causes that object to change shape.

Fact 2: Folds are usually caused by compressional forces.

Given the two facts above, answer the question "What force causes an object to change shape?" with the following options: 
- quadriceps
 - Electrical energy
 - mechanical
 - Heat energy
 - friction
 - compressional
 - flow of electrons
 - kinetic energy


 

      compressional   