In which instances do you have to approach a pedestrian crossing with particular care?

You are correct in selecting all three situations. According to German traffic rules, you must approach pedestrian crossings with particular care if pedestrians want to cross, because you must always give way to them. If the view of the crossing is restricted, you need to slow down and be prepared to stop since you may not see pedestrians early enough otherwise. Also, if another vehicle is already stopped at the crossing, it indicates that they are yielding to pedestrians, so you must also stop and wait because pedestrians may be crossing or about to cross. These rules help ensure pedestrian safety at crossings.