It is mandatory to use high-beam headlights when travelling at more than 40 km/h on a road that is...

A)insufficiently lit, inside or outside a built-up area.
B)an interurban road that is sufficiently lit.
C)an interurban road that is insufficiently lit.Correct
Every vehicle equipped with high-beam or main-beam headlights travelling at more than 40 km/h, between sunset and sunrise, outside built-up areas, on insufficiently lit roads, or at any time of day through tunnels, underpasses and road sections affected by the tunnel sign that are insufficiently lit, shall have the high-beam headlights switched on, except when dipped headlights or low-beam headlights must be used, especially to avoid dazzling other road users.
High-beam headlights are completely prohibited in built-up areas.