Are you sure you are qualified for this job?
I emphasized on you to be careful in answering questions like this. The question presented to dig or at least map out your qualification in certain occupations and this will of course be an important consideration for the interviewer to let you pass or not.
Here, I have two alternative answers that I find as the most effective:
- This is the job that I wanted to do and I have studied with my best to ensure that I had the potential and the skills needed to finish this job.
- In order to make you believe with my competence, you can test me!
If you are really mastering (advance) that field, I suggest you to choose the second alternative answer. That answer is the most optimistic and has a strong suggestion on the interviewer.