When can the soil effect occur?

Question

Question EASA Drone Quiz - Flight performance and planning

QuizVDS · Accepted Answer

Close to the ground (height less than one rotor diameter/wingspan)

QuizVDS · Answer

At high altitude

QuizVDS · Answer

Approximately 25 metres above the ground

QuizVDS · Answer

None of the previous answers is correct

Id 56 - EASA Drone Quiz – Drone Pilot Certification - When can the soil effect occur?