I just did this exercise in Tae Kim’s guide to Japanese and I feel like dome questions like this one are up to interpretation regarding what particle to use. In that case, in Alice’s second dialogue I had assumed that the answer was が because in my head, the library is the subject all this time, and Alice is just a bit confused after Bob points out where it is. Is my interpretation also correct? If not, how can I know how to choose which one?
by AutisticAndy18