Which statement is true regarding movable lights on a vehicle?

The statement that all lights must be fixed is correct because vehicle lighting must meet specific safety regulations. Fixed lights, such as headlights, taillights, and turn signals, are designed to provide consistent visibility and communication to other drivers and pedestrians without the risk of inadvertently blinding or distracting them. Movable lights, which may adjust for various conditions, like off-road driving or heightened visibility, are often regulated and limited to specific applications where safety is maintained.

The other statements suggest options that could lead to confusion or safety issues. For instance, if lights could be adjusted while driving, it might divert the driver's attention from the road. Indicating that only headlights are movable ignores the fact that some vehicles may have additional adjustable lighting mechanisms, but does not imply that they are universally allowed or appropriate. Additionally, while some lights may have a movable aspect for safety, the key principle remains that all standard lighting needs to be fixed for the primary driving scenarios to ensure proper function and safety compliance.