To pass this question, you have to convince them that you are going to stick around. This isn't a question to see what you know or what your philosophy is, it is a concern they have that you have to address. Your persuasion skill will be required for this answer. But if you can't be persuasive, convince them through step by step facts that leads to the fact that you are going to stay with this company if they hire you.
This answer is a little long, but if you don't convince them that you are going to stay long, then you have a very little chance of being hired. So take whatever time you need to convince them. If you think of your own answer, write it down and be able to say it smoothly so they can fully understand that you are serious about staying.