It allowed them to travel at a decent price, possibly to an area with better job opportunities.
The answer should be the Radula
I think it would be A if anything
The most obvious reason is that one has to pack up and go because things are not so good at home. Long ago, that probably meant that the climate had changed and made life impossible. It might have become too hot or too cold or too wet, which in turn would have affected not only quality of life but also make survival a shaky proposition. Drought, flood, and temperature changes could certainly push people to move on.
I hope that helped a little.
