Final answer:
The truck should be positioned 25 feet away from the wall when adjusting the aim of a headlamp assembly using a wall adjustment screen.
Step-by-step explanation:
When adjusting the aim of a truck headlamp assembly using a wall adjustment screen, the truck should be positioned 25 feet away from the wall.
This distance is determined based on the maximum distance at which the eye can resolve two headlights, which is 1.3 meters. Therefore, the truck needs to be positioned at a distance that allows the headlamp assembly to simulate the distance between the headlights.
By aligning the truck 25 feet away from the wall, the headlamp assembly's aim can be adjusted accurately.