In what situation is it especially dangerous to perform a turn?

Your answer is correct because all three situations present limited visibility or increased difficulty in judging the environment, making turns especially dangerous. Turning before the crest of a hill is risky because you cannot see oncoming traffic or obstacles behind the hill, increasing the chance of collision. Turning before bends in the road is dangerous for similar reasons—your view of approaching vehicles or pedestrians is obstructed, so you may misjudge the safety of the turn. In foggy conditions, visibility is greatly reduced, making it harder to see other road users or road features, increasing the risk during a turn. In German traffic rules, it is essential to have clear visibility before turning to ensure safety for yourself and others.