There are many people who do not change their jobs for years and when they go out looking for a new employer, this is one of the most important questions they are asked. Some people might look upon staying with the same employer for long as "lack of ambition".

A good answer to this question can be something like, "Yes, you are right. I stayed with my last employer for almost 5 years but I was continuously growing in the company, doing new things, handling bigger challenges. So, I was quite happy working with them for these many years." You can then talk about how you grew with your last employer.