You can answer this question in numerous ways. But to make your answer effective, you should think of an answer that will show your strong points as a salesman. Make sure to cover your own traits that are important to sales. Here is an example.
This is a simple short answer. Not everyone can be a salesperson. They need to have the right personality such as good communication skills. You don't have to have a great answer for this question. But the most important aspect is showing that you enjoy sales.