You are presented with the question "Powering what with a battery requires a path for electricity to flow?" and the following answer choices: 
- closed
 - energy
 - complete
 - vehicles
 - engines
 - a phone
 - buses
 - Cars

Now knowing that powering an electrical device with a battery requires a path for electricity to flow through a closed circuit and today's cellular phones are second-generation devices, choose the best answer.


 

      a phone   