When must attached working equipment be marked with red-white warning plates?

Your selected combination is entirely correct because each condition in the options is a specific requirement under German traffic regulations regarding marking equipment attached to vehicles.

1. Equipment that has parts presenting a danger to traffic must be marked to alert other road users to potential hazards.
2. When equipment extends laterally more than 40 cm beyond the side lights or rear lights of the tractor, this marking is necessary to ensure visibility and safety.
3. Additionally, any extension of more than 1 meter to the back beyond the rear lights of the tractor also requires marking, as it poses a significant risk in terms of rear visibility and safety for following vehicles.

Failing to mark such equipment can lead to dangerous situations on the road, so adherence to these marking requirements is crucial for the safety of all road users.