Which groups were considered to be master builders

Which would make the best heading for this list of notes about the migration of african-americans during the reconstruction era?

Aheard of sheep moves up in the mountain to graze during summer and migrated to the valley during winter what type of migration do the sheep 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