Which daily inspection set is required to keep a combination in technically safe condition under IAAA Category E Theme 4?

1. Only the tractor oil level, because the trailer is inspected annually
2. Compulsory checks of the coupling, brakes (including air or hydraulic links), lights, signalling and other items that keep the combination technically safe
3. Only a visual glance at the trailer paint
4. No daily checks; IAAA inspects every combination at the roadside instead