Mongols favored trade even before Ghenghis khan, they hunted/herded very few were weapon makers or potters/weavers, many items they needed to living had to be traded. As Ghenghis khan rose to he realized the Mongol army was gonna need many things for battles. To facilitate trade Ghenghis offered protection to merchants that came from east and west, offered higher status for merchants allowed by the Chinese or Persians who despised trade and traders.
I have no clue of "which of the following" because i cannot see the answers but,
The Great Migration, or the relocation of more than 6 million African Americans from the rural South to the cities of the North, Midwest and West from 1916 to 1970, had a huge impact on urban life in the United States. Driven from their homes by unsatisfactory economic opportunities and harsh segregationist laws, many blacks headed north, where they took advantage of the need for industrial workers that first arose during the First World War. As Chicago, New York and other cities saw their black populations expand exponentially, migrants were forced to deal with poor working conditions and competition for living space, as well as widespread racism and prejudice. During the Great Migration, African Americans began to build a new place for themselves in public life, actively confronting economic, political and social challenges and creating a new black urban culture that would exert enormous influence in the decades to come.
Ecological release refers to a population increase or population explosion that occurs when a species is freed from limiting factors in its environment
I think it was Robert Walpole.