If a truck has a solid white line in its lane, what should it do?

Answer: C — Should not cross the line.

When a truck encounters a solid white line in its lane, the correct action is to not cross the line. Solid white lines are used to indicate that lane changes are discouraged or not permitted. This is especially important for larger vehicles like trucks, as changing lanes inappropriately can lead to dangerous situations due to their size and limited maneuverability. By adhering to this rule, the truck ensures its own safety as well as the safety of other road users. Maintaining the position within the lane helps to prevent accidents and promotes smoother traffic flow, particularly in areas where lane changes might create conflicts, such as near highway merges or in busy urban environments. In contrast, crossing a solid white line could lead to illegal maneuvers and create hazards on the road. Thus, avoiding any crossing of a solid white line is crucial.