I answered honesty and used it to my benefit. I identified my top choices and referenced the central mission that attracted me to the group of schools (don't BS...they will see right through it). I would then use that to lead into how part of the process of applying to medical school is not only searching for an institution that identifies me as a good fit, but that another important factor is determining the correct school to fit with me-symbiotic relationship, synergetic...whatever.
Also-I used my acceptances to my advantage as well. I said with every bit of conviction (because I meant it), during my interview at ECU-Brody School of Medicine, if there came a day that I received an acceptance letter from ECU, I would cancel all other acceptances and interviews to immediately sign on the dotted line. I then quickly explained why Brody was my top choice-didn't suck up, didn't come across as cocky-it was my goal and I stated it with passion and clarity. Hopefully this helps!