Pretty much if you can find it in the classical section of a record store, it's fair game. So Bach, Debussy, Stockhausen, Xenakis, Ravel, Brahms, Verdi, Glass, etc.
If it's not popular music (e.g., pop artists, soundtrack composers, jazz) then you're good to go. Jazz might be acceptable if the piece in question was recorded before, say, 1970 or so. I'd stick with "classical" composers pre-1960, or agreed-upon current "masters" like John Adams, Steve Reich, and Terry Riley.
Basically, they're looking to see if you know who the composer is, the period/school he belongs/belonged to (e.g. baroque, serialists, minimalist, impressionists, and the approximate year it was), what musical form the piece is in (rondo, sonata allegro, suite). Basically, are you musically literate - you know that Bach was a Baroque composer in the early 1700's, you understand what a fugue or cantata is, basic opinions on the piece's strengths and weaknesses, if any. You're trying to show that you've listened to music, thought about it, and can articulately express an opinion and justify it.
Look for answers to these questions: What's interesting to you about these pieces? Why do you care about them? Why should they be interesting to someone else? What was going on in the composer's life at the time? Were there any cultural issues affecting the piece? What form do these pieces have? Is there any innovate approach to the form or harmony? For example, BVW 846 has an interesting atypical form, and the theme is introduced in whole 22 times and in part 2 more. Bizet found out he actually quoted a piece written less than 10 years earlier which he'd mistaken for a folk song. (Got all that in a few minutes of Googling on the pieces and composers. Have you tried that yet?)
If these aren't pieces that you've been interested in enough to have gone out and learned stuff about - both the pieces themselves, the circumstances surrounding their composition, first performances, who they were written for, the roots of the themes, what new ground was broken in their writing, how instruments affected the music and vice versa - then they may not be the right pieces for you to talk about.
I think this part of the interview is to find out if you've taken on investigating a piece and finding out all you can about it, its history, and its cultural matrix and significance - cross-analysis of the music and the composer and how each affected the other. That's what you need to do, and searching on analysis and history along with the pieces and composers should give you what you need.
