In the dark hour of the day, the bus moving in the unlit parts of the road along the defined route should use

Explicación

The English option texts diverge from the source editions: the accepted source response permits either dipped or main beam on an unlit road, whereas English says both must be used together. The appropriate beam depends on traffic conditions; main beam must be dipped to avoid dazzle, while permanently limiting the bus to dipped light is also too narrow.