When must you use dipped headlights also during the day?

You answered correctly. Dipped headlights must be used during the day when visibility is reduced, such as in cases of fog, falling snow, or rain. These weather conditions make it difficult for you to see and for others to see you, so using dipped headlights increases safety. However, a misted windscreen does not require dipped headlights as it's an issue only affecting your own visibility, not how visible your vehicle is to others. For future questions, remember to use dipped headlights whenever visibility for all road users is impaired by weather conditions, not just by issues inside the car.