What must you do to avoid soiling the roadway?

You answered correctly by selecting to remove loose earth from the tyres before leaving the field and to clean working equipment before leaving the field. According to German traffic rules, this is important to avoid soiling the roadway, which can create hazardous driving conditions for other road users. Loose soil or mud on tyres and equipment can easily be transferred onto public roads, making them slippery. Cleaning helps maintain road safety and prevent fines for dirtying the road. The third option, about using twin tyres when it rains, does not directly relate to preventing soiling but rather to traction in wet conditions, so it is not required for this question.