While it is not necessarily, inappropriate, do not forget your job during the interview is to convince the interviewer you want to attend his or her school. It would not be ideal to lose your composure or excitement due to an answer you do not like, especially during a high-stakes interaction.
These are also not questions that make good use of your limited time with the interviewer. You should have an opportunity to ask about rank and grading throughout your interview day. Be sure to listen closely during the tour, as they may freely disclose this information. These are factors that are important to many students.