Which lights should motorcycles use during the day?

Why this is the correct answer

Spanish traffic regulations specifically require motorcycles to ride with dipped headlights (low beams) on at all times — day and night — on any public road. This is the key rule for this question. Sidelights (position lights) are part of the motorcycle's mandatory lighting equipment and they do switch on automatically along with the dipped headlights, but they are NOT what the law specifically requires for daytime use. Sidelights alone would be insufficient because they are too dim to make a motorcycle clearly visible to other drivers. That is why option B (sidelights and dipped headlights) is incorrect: the regulation does not require sidelights as a specific daytime obligation — it only mandates dipped headlights. The purpose of this rule is to improve the visibility of motorcycles, which are smaller and harder to spot than cars. Most modern motorcycles automatically turn on the dipped headlights when the engine starts, precisely to comply with this requirement. Failure to use dipped headlights during the day can result in a fine of up to 200 euros and the loss of 3 licence points.