What are your career plans for the next five years?

Your employer (or future employer) wants to find out how smart and ambitious you are, as well as your goals and your abilities and also to check if you are ready to work hard for promotion in the company. So you need to make an impression, but still be yourself and be honest about the whole thing. You could say something like: "I am prepared to work hard and learn as much as I can in order to do my best. I expect to get on well with my colleagues and will take their advice and benefit from their experience. Also, I want to make sure that I am aware of the current news and advancements in our field so I will try and stay updated in every possible way. I am definitely not afraid of work nor new challenges". Of course, if you do not mean any of that, you will not sound convincing and will be turned down after your interview. Even if you make it and get the job, you have to prove what you said in order to keep your job... don't forget that! Hope this helps! And very good luck to you!