Answer:
(B) Civil War veterans
Step-by-step explanation:
Former slaves: After the Civil War and the abolition of slavery, many former slaves sought opportunities for land ownership and a better life on the Great Plains.
Northern Europeans: Many immigrants from Northern Europe, including Scandinavia and Germany, migrated to the Great Plains in search of agricultural opportunities and a new start.
Mexicans: Mexican immigrants and Mexican-Americans were part of the migration to the Great Plains, contributing to the region's cultural and agricultural diversity.
However, Civil War veterans were not a specific group that migrated to the Great Plains as a result of their veteran status. While some veterans may have relocated to the region after the war, they were not a distinct group participating in a mass migration to the Great Plains in the same way that former slaves, Northern Europeans, and Mexicans were.