Question

according to the
o - zone\ rule, how can you ensure a truck driver can see your vehicle?
stay at least three car lengths behind the truck.
flash your headlights whenever the truck is in motion.
maintain enough distance so you can see the truck driver in the side mirror

Explanation:

The "no - zone" rule in truck - car visibility: The key is to be in a position where the truck driver can see the vehicle. Staying at least three car lengths behind doesn't ensure visibility. Flashing headlights isn't a standard "no - zone" rule - related method for ensuring the truck driver can see you. If you can see the truck driver in their side mirror, it means the truck driver can likely see your vehicle too, as the side mirror's field of view allows for reciprocal visibility in this context.

Answer:

The option "Maintain enough distance so you can see the truck driver in the side mirror" (the third option in the list).