The interviewer is trying to figure out whether or not you are going to be a long term employee or whether or not you will be using this job as a stepping stone to another objective. So, you should try to assure him/her that your intention is to stay with the company and to grow in your career within the company. You should respond "I am looking for a position with a company where I can stay and grow with and I feel this position would give me this opportunity."