The candidate may ask you what you thought of their interview. You should have planned an answer to this in the planning section of Chapter 1, Before the Interview – Preparing and Practicing.
Do not say you have or haven't got the job! That decision can only be made after seeing all the candidates and adjudicating the scores.
The candidate may ask about a specific skill and what more they can say to raise their score. You should answer honestly and give the candidate an opportunity to expand on their previous answer. Keep one eye on the clock though!