Which factor is most likely to cause a large-scale human migration from one region to another?

The correct answer to the question "Which factor is most likely to cause a large-scale human migration from one region to another?" is Option C: Widespread political instability and persecution.

The other options — A) A slight increase in local property taxes, B) Improved public transportation within a city, D) A new cultural festival in a neighboring town — are incorrect for this GED Exam Prep question. As explained above: Significant push factors like political instability, war, persecution, or natural disasters often force large populations to migrate in search of safety, security, and better living conditions.