Settlement depended of several variables like geography. Since that they depended a lot of hunting, they needed some geographical standard to be able to hunt and to build villages far from their resources. So, if in the settle region wasn't enough animals to hunt, they needed to change place. That's why they were considered as nomads.
Usually, back then, they followed their food and tracked them without settling too long in one place. But since that's not one of the answers I would go with A.
