Fact 1: Electric devices require electrical energy to function.

Fact 2: Lie detectors are electrical or mechanical devices.

Given the two facts above, answer the question "what requires electrical energy to function?" with the following options: 
- vehicles
 - h2o
 - oxygen
 - Something to move
 - critical organs
 - carbon
 - nervous system
 - lie detectors


 

        lie detectors 