literally answering this over a year later but in the story that it gives that this person didn't show, it says that memory is VAGUE. Then it goes on talking about rooms and how the human mind leaves out details. So I think it's A VAGUE
A disadvantage of using a poster would that it may, potentially, go unnoticed. For example, if a poster was hung up in the busy halls of a school, the students may not take the time to study it because they are in a hurry to get to class.
Furthermore, most handwashing education takes place among younger children, typically kindergarteners or 1st graders. If a poster was hung up in an elementary school with the goal of educating the younger kids, it may fail because many younger children do not know how to read yet. Hope this helps!