This question will have followed a previous one discussing the number of interview applications you have made. You will probably have given an answer to say that you have applied to lots of places.
The best way of giving you advice on this is to take a step back and go to the previous question which in all likelihood you have probably answered incorrectly by giving away that you have applied to lots or places.
However, if you find yourself in this situation the best way of answering it is probably to dig yourself out of the hole and concentrate on something positive about the interviews you have had or if not to get the conversation back to the interview you are currently having. Something along the lines of this may suffice.
Examples of Answers
“I have a number of applications outstanding at present and anticipate a response in the next few weeks. However I am very keen to progress my application with your company and hope that you think I am a good fit.”
“It is a difficult market at present and I am very grateful for you giving me the opportunity to be interviewed here. I think that my skills and experience fit the job description you have and I hope you see this as well.”
There is no right or wrong approach to this question as it is one asked when you have gone down the wrong route by revealing the number of interviews you have had. Try to deflect any attention away from the number of interviews you may or may not have had and onto the present interview.