When should dipped headlights be used?

Dipped headlights should be used when driving in poor conditions, such as fog, rain, or snow, as well as at night when visibility is reduced. They are also used to reduce glare for other drivers. Options A and B are incorrect because parking and daytime running lights do not require the use of dipped headlights. Option D is incorrect because signaling does not involve the use of headlights.