Which of the following vehicles qualifies as a self-propelled agricultural machine (selbstfahrende Arbeitsmaschine) under KFG 1967?

1. A combine harvester (Mähdrescher) with a design speed up to 50 km/h
2. A standard farm tractor towing a grain tipping trailer
3. A commercial flatbed truck carrying round bales of hay
4. A four-wheel-drive pickup truck used on a forestry estate