Energy can be converted into mass. Friction reduces the efficiency in a system. The amount of energy in a system remains constant. Potential energy can be converted into kinetic energy.
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: A perpetual motion machine is a theoretical device which, once started, continues to operate without any additional input of energy. Which statement describes why a perpetual motion machine is impossible to design?
Possibilities:
- Energy can be converted into mass.
- Friction reduces the efficiency in a system.
- The amount of energy in a system remains constant.
- Potential energy can be converted into kinetic energy.

Friction reduces the efficiency in a system.