What major historical event caused the force mass-migration of people in Document #3

When conducting research for forming a hypothesis, which practice should historians follow?

Interest groups representing businesses and investors are often among the most successful lobbying groups for all of the following reasons, except a. such groups have the financial resources to mount sustained campaigns on their own behalf b. these groups' members contribute heavily to many legislators' campaigns and in so doing gain greater access to legislators c. these groups have often been in existence for decades, allowing them to both master the legislative system and develop close ties with legislators d. the members of these groups make up the majority of voters in many districts

Demographers can compare a choropleth map to a to understand how geography influences population distribution and there are no a, b,c, or d u have to find it out ur self asap