The task & goals
In this item, students are asked to rank the strength of the field at various points. We anticipate that students might attend to the distance from the center of the magnet, might consider the "North" pole to be the source of the field (based on drawings in which field lines are directed out of the north pole), or might only consider the distance to the magnet itself, and not to the end of a pole.
For teachers, we would hope that they would interpret students' ideas not just as incorrect, but what students are attending to that are consistent with this or related models, and draw a comparison or build on those ideas.
Student responses
This student pictures field lines and the potential energy that might reasonably be associated with those. So although the density of lines is equally strong at A and B, they have just "left" the magnet at B and so have more energy than at A. Being able to articulate and interpret that idea from the student writing would be, I think a strong signal of intellectual empathy and analysis.
Here, the student thinks of a magnet the way one might (at first order) think about gravity - simply looking at the distance to the center of the magnet.