Every time you respond to an interviewer's question, you should be trying to demonstrate your qualifications, experience, and expertise. Keep in mind that the purpose of an interview is to further qualify you for this role. The interviewer knows that you can do this job based on the information you provided in your resume or CV. They want to confirm this information and explore your background in more depth. Remembering this throughout the interview will help improve your performance and make it more likely you will be offered the position at the conclusion of the interview.