Final answer:
The EMS providers' first action should be to tell the car's occupants to stay in the car.
Step-by-step explanation:
When arriving at the scene of a car accident where an electrical wire has fallen on top of the car, the EMS providers' first action should be to tell the car's occupants to stay in the car. This is because the car's metal body acts as a Faraday cage, which means that the electrical field inside the car is zero. Even if the wire is active, the inside of the car will be unaffected as long as the occupants remain inside.