What’s the Definition of reunification

Restoration of political unity to a place or group, especially a divided territory

Ibelieve the answer is b cause its only saying what they were focusing on,not a hardship

One of the things that allowed native americans in mexico to settle cities larger than those in areas to the north was "b. the development of cities that were built by an earlier civilizations," since mexico had been the home of some of the world's most advanced civilizations before the columbian invasion