Answer: c) use a person outside the vehicle to help you if possible.
Explanation:
Back up is the mechanism which is followed by the vehicle for reversing. It is also known as reversing operation.A driver can use rear view mirror and a person outside the vehicle for watching the nearby vehicle and road for safe reverse.
Outsider can provide the exact guidance to back up the vehicle as he/she can clearly see every small element and thus can provide reversing instructions accordingly to the driver .
Other options are incorrect because at time small objects and children aren't visible to the drive and that might cause accident. Side mirrors and rear view mirror are helping equipment present in the car but even though they can miss showing the small element.Thus the correct option is option(c).
