Fact 1: An automobile engine transforms chemical energy into mechanical energy.

Fact 2: Engines convert some energy of it to move the pistons (to work).

Given the two facts above, answer the question "What is moved by mechanical energy in an automobile?" with the following options: 
- vehicles
 - brake pad
 - humans
 - animals
 - people
 - gas pedal
 - pistons
 - seatbelt


 

       pistons  