Answer:
Slavery/extension states; rights
Step-by-step explanation:
Slavery became highly predominant in the South because it aided the rapid growth and boom rooted in the huge cotton and sugar plant as a result of having enough manpower for the plantations.
There was however a revolution and protests which helped in the abolition of slavery and ensure everyone had equal rights.
This was why McClure said that one of the issues the founders did not foresee was the fact that the South moved from slavery/extension states to rights.