The other didn’t give any explanation so in case you need that,
Look at the options and try to imagine how it could be each one. Then, once you do that, simply pick which one makes the most sense. It wouldn’t be the route the speaker took because he is already in the foyer. And it can’t be different people who used the library because he didn’t describe a single person in the whole poem. It almost looks like it could be how to look up a book because if you look at the first two lines, they could be used as landmarks to find your way to the card catalogue, but then he begins to describe other things which would make the “directions” just a bunch of gibberish about the library. Leaving only one answer left, C
