Where are you allowed to park a trailer with a permissible total mass exceeding 2 t in built-up areas regularly on sundays and public holidays and between 10 p.m. and 6 a.m.?

The selected combination is correct because the German traffic regulations allow parking a trailer with a permissible total mass exceeding 2 tons in specific areas during certain times.

1. In industrial areas, trailers can be parked because these areas typically have fewer restrictions to facilitate commercial activities.
2. In wholly residential areas, on specially designated parking spaces, parking is permitted as such spaces are established to accommodate vehicles while ensuring they do not disturb residents.

The reason for needing to include both options is that the regulations are designed to maintain order and safety in traffic, addressing where larger vehicles can park without interfering with regular traffic flow or residential life. Not including all relevant options may lead to misunderstanding where parking is allowed, potentially leading to fines or towing.